Clockwise from top left U.S. soldiers engaging the retreating Mexican force during the Battle of Resaca de la Palma, American victory at Churubusco outside Mexico City, U.S. marines storming Chapultepec castle under a large American flag, Winfield Scott entering Plaza de la Constitución after the Fall of Mexico City.
| United States
|Commanders and leaders|
| James K. Polk
Stephen Watts Kearny
John D. Sloat
William J. Worth
Robert F. Stockton
Matthew C. Perry
John C. Fremont
William B. Ide
| Antonio López de Santa Anna
Pedro de Ampudia
José María Flores
Mariano G. Vallejo
José Joaquín de Herrera
Martin Perfecto de Cos
Pedro Maria de Anaya
Agustin Jeronimo de Iturbide y Huarte
Manuel Pineda Muñoz
1848: 32,000 soldiers
|c. 34,000–60,000 soldiers|
|Casualties and losses|
|1,733 killed in battle
13,283 total dead
|c. 16,000 soldiers|
Part of a series on the
|History of the
|United States portal|
Part of a series on the
|History of Mexico|
A war between the U.S. and Mexico spanned the period from spring 1846 to fall 1847. The war was initiated by the United States and resulted in Mexico's defeat and the loss of approximately half of its national territory in the north. In the U.S. the war is termed the Mexican–American War, also known as the Mexican War, the U.S.–Mexican War or the Invasion of Mexico. In Mexico names for the war include Primera intervención estadounidense en México (United States' First Intervention in Mexico), Invasión estadounidense a México ("United States' Invasion of Mexico"), Guerra de la Invasión estadounidense, and Guerra del 47 ("The War of 1847").
After its independence in 1821 and brief experiment with monarchy, Mexico became a republic in 1824, characterized by considerable instability, so that when the U.S. initiated the conflict with the Centralist Republic of Mexico, Mexico was ill-prepared to respond. The war with the U.S. followed in the wake of decades of Indian raids in the north of Mexico, which Anglo-American migration to the Mexican province of Texas was aimed at buffering. Anglo-Americans and some Mexicans revolted against the Mexican government in the 1836 Texas Revolution, creating a republic not recognized by Mexico, which still claimed it as its national territory. The 1845 expansion of U.S. territory with its annexation of Texas escalated the dispute between the U.S. and Mexico into open war.
U.S. forces quickly occupied Santa Fe de Nuevo México and Alta California Territory, then invaded parts of Northeastern Mexico and Northwest Mexico; meanwhile, the Pacific Squadron conducted a blockade, and took control of several garrisons on the Pacific coast farther south in Baja California Territory. Another U.S. army, under General Winfield Scott captured the capital Mexico City, marching from the port of Veracruz, virtually unopposed.
The war ended in a victory for the United States. During this period, the leadership of the Mexican Army changed frequently. Political factionalism was intensely divisive and led at one point to open civil war in the capital.
The 1848 Treaty of Guadalupe Hidalgo ended and specified the major consequence of the war: the forced Mexican Cession of the territories of Alta California and Santa Fe de Nuevo México to the United States in exchange for $15 million. In addition, the United States assumed $3.25 million of debt owed by the Mexican government to U.S. citizens. Mexico recognized the loss of Texas and thereafter cited the Rio Grande as its national border with the United States.
American territorial expansion to the Pacific coast had been the goal of U.S. President James K. Polk, the leader of the Democratic Party. The war was highly controversial in the United States, with the Whig Party, anti-imperialists and anti-slavery elements strongly opposed. Critics in the U.S. pointed to heavy casualties of the U.S. forces and high monetary cost of the conflict. The war raised the slavery issue in the United States, leading to intense debates that led to the bloody civil war. In Mexico, the war came in the midst of political turmoil, which increased into chaos during the conflict. The military defeat and loss of territory was a disastrous blow, causing Mexico to enter "a period of self-examination ... as its leaders sought to identify and address the reasons that had led to such a debacle." The shift in the Mexico-U.S. border left many Mexican citizens separated from their national government. For the Indians who had never accepted American or Mexican rule, the change in border meant conflicts with a new outside power.
- 1 Roots of the Conflict
- 2 Foreign Designs on California
- 3 Anglo Colonization in Texas and the Texas Revolution
- 4 Prelude to War
- 5 Challenges in Mexico
- 6 United States Combatants
- 7 Outbreak of the War
- 8 Reaction in the U.S.
- 9 Conduct of the war
- 9.1 New Mexico Campaign
- 9.2 California Campaign
- 9.3 Pacific Coast campaign
- 9.4 Northeastern Mexico
- 9.5 Northwestern Mexico
- 9.6 Tabasco
- 9.7 Desertion from U.S. Army
- 9.8 Scott's Mexico City campaign
- 9.9 San Patricios
- 9.10 Santa Anna's last campaign
- 9.11 Mexican guerrilla campaign
- 10 Treaty of Guadalupe Hidalgo
- 11 Results
- 12 Impacts of the war in the U.S.
- 13 Impact of the War in Mexico
- 14 See also
- 15 Notes
- 16 Bibliography
- 17 External links
Roots of the Conflict
Having attained independence from Spain in 1821, Mexico contended with internal struggles that sometimes verged on civil war. In the sparsely settled interior of northern Mexico, the end of Spanish colonial rule was marked by the end of financing for presidios and for subsidies to Indian groups to maintain the peace. There were inter-Indian conflicts in the northern region as well. The Comanche being particularly successful in expanding their territory in the Comanche-Mexico Wars and garnering resources. The Apache-Mexico Wars also made Mexico's north a violent place.
Hostile Indian activity also made communications and trade between the interior of Mexico and provinces such as Alta California and New Mexico difficult. As a result, New Mexico was dependent on the overland Santa Fe Trail trade with the United States at the outbreak of the U.S.-Mexican War.
The military and diplomatic capabilities of Mexico declined after it attained independence and left the northern half of the country vulnerable to the Comanche, Apache, and Navajo Indians. The Indians, especially the Comanche, took advantage of Mexico's weakness to undertake large-scale raids hundreds of miles deep into the country to acquire livestock for their own use and to supply an expanding market in Texas and the United States.
The Mexican government's policy of settlement of Anglo-Americans in its province of Texas was aimed at expanding control into Comanche lands, the Comancheria. Instead of settlement occurring in the central and west of the province, Anglo-Americans settled in east Texas, where there was rich farmland and which was contiguous to southern U.S. states. Settlers poured in and Mexico took steps to discourage further settlement.
In 1836 Mexico was relatively united in refusing to recognize the independence of Texas. Mexico threatened war with the United States if it annexed Texas. Meanwhile, U.S. President Polk's assertion of Manifest Destiny was focusing United States interest on westward expansion beyond its existing national borders.
|This article may need to be rewritten entirely to comply with Wikipedia's quality standards. (November 2015)|
Foreign Designs on California
During the Spanish colonial era, the Californias, the Baja California peninsula and Alta California, were sparsely settled. In the second half of the eighteenth century, Spain became concerned that this territory, which it claimed but it did not effectively settle, could be taken by foreign powers. It then embarked on new policies to secure its northern coastal region, which it had earlier implemented in the interior of Mexico's north: the creation of missions and presidios. Missions were congregate Indian peoples, convert them to Catholicism, and teach them civilized ways. Presidios were military posts to secure territory and establish Spanish sovereignty, pacify Indian peoples, and help attract civilian settlers. Missions and presidios were established in coastal California, and civilian settlement increased there. The interior of California and northern California were claimed but not controlled by the Spanish crown. Missions and presidios were funded by the Spanish crown.
By the late eighteenth century, Alta California became the economic center and the Spanish crown moved its administrative center from Loreto, in Baja California, to Monterery in 1777. Civilian settlement followed in San José de Guadalupe (now San Jose, CA), founded by Governor Felipe de Neve. The governor also promulgated the "'Regulations for the Governance of California,' a set of laws and regulations ... that became California's first constitutional corpus." Some missions and presidios became the core for settlements that later became major cities. When Mexico won its independence from Spain in 1821, California became Mexican territory, still a marginal region far from the national capital of Mexico City.
Before Mexican independence in 1821, 20 land grants had been issued (at little or no cost) in all of Alta California, many to "a few friends and family of the Alta California governors." The 1824 Mexican General Colonization Law established rules for petitioning for land grants in California; and by 1828, the rules for establishing land grants were codified in the Mexican Reglamiento (Regulation). The Acts sought to break the monopoly of the Catholic Franciscan missions and possibly entice increased Mexican settlement. Research shows that the majority of rancho grants were given to retired non-commissioned soldiers. The largest grants to Nieto, Sepulveda, Domínguez, Yorba, Avila, Grijalva, and other founding Californio families were examples of this practice.
Many foreign residents of California in the Mexican period also became rancho grantees. Some were "Californios by marriage" like Abel Stearns (who was naturalized in Mexico before moving north) and the Englishman William Hartnell. Others married Californios but never became Mexican citizens. Rancho ownership was possible for these men because, under Spanish and then Mexican law, married women could independently hold title to property. In the Santa Cruz area, three Californio daughters of the inválido José Joaquín Castro (1768–1838) married foreigners yet still received grants to Rancho Soquel, Rancho San Agustin and Rancho Refugio.
A U.S. diplomatic mission in 1829, led by Anthony Butler, attempted to bribe the Mexican government to give the port of San Francisco to the United States, as well as to cease claiming territory near what was then the U.S.-Mexican border (which is now roughly the boundary between Louisiana and Texas).  The Mexican secularization act of 1833 under the administration of liberal Valentín Gómez Farías turned much of the Spanish missions in California into large Ranchos of California, owned by Mexican settlers, and also undermined the power of the Roman Catholic Church, a key aim of the liberals in Mexico. Secularization brought new settlers into Alta California.
In 1842 the U.S. minister in Mexico, Waddy Thompson, Jr., suggested Mexico might be willing to cede Alta California to settle debts, saying: "As to Texas, I regard it as of very little value compared with California, the richest, the most beautiful, and the healthiest country in the world ... with the acquisition of Upper California we should have the same ascendency on the Pacific ... France and England both have had their eyes upon it."
U.S. President John Tyler's administration suggested a tripartite pact that would settle the Oregon boundary dispute and provide for the cession of the port of San Francisco from Mexico; Lord Aberdeen declined to participate but said Britain had no objection to U.S. territorial acquisition there.
The British minister in Mexico, Richard Pakenham, wrote in 1841 to Lord Palmerston urging "to establish an English population in the magnificent Territory of Upper California", saying that "no part of the World offering greater natural advantages for the establishment of an English colony ... by all means desirable ... that California, once ceasing to belong to Mexico, should not fall into the hands of any power but England ... daring and adventurous speculators in the United States have already turned their thoughts in this direction." But by the time the letter reached London, Sir Robert Peel's Tory government with a Little England policy had come to power and rejected the proposal as expensive and a potential source of conflict.
A significant number of influential Californios were in favor of annexation, either by the United States or by Great Britain. Pío de Jesús Pico IV, the last governor of Alta California, was in favor of British annexation. 
Anglo Colonization in Texas and the Texas Revolution
In 1800, the colonial province of Texas was sparsely populated, with only about 7,000 non-Indian settlers. The Spanish crown developed a policy of colonization to more effectively control the territory. After independence, the Mexican government implemented the policy, granting Moses Austin, a banker from Missouri, a large tract of land in Texas. Austin died before he could bring his plan of recruiting U.S. settlers for the land to fruition, but his son, Stephen F. Austin, brought over 300 Anglo American families into Texas. This started the steady trend of migration from the United States into the Texas frontier. Austin's colony was the most successful of several colonies authorized by the Mexican government. The Mexican government intended the new settlers to act as a buffer between the Tejano residents and the Comanches, but the Anglo colonists tended to settle where there was decent farmland and trade connections with Louisiana, which the U.S. had acquired in the Louisiana Purchase, rather than further west where they would have been an effective buffer against the Indians.
In 1829, as a result of the large influx of immigrants from the U.S., the Anglos outnumbered native Spanish speakers in the Texas territory. President Vicente Guerrero, a hero of Mexican independence, moved to gain more control over Texas and its influx of southern white Anglo colonists and discourage further immigration by abolishing slavery in Mexico. The Mexican government also decided to reinstate the property tax and increase tariffs on shipped U.S. goods. The settlers and many Mexican businessmen in the region rejected the demands, which led to Mexico closing Texas to additional immigration, which continued into Texas illegally, nonetheless, from the United States.
In 1834, General Antonio López de Santa Anna became the centralist dictator of Mexico, abandoning the federal system. He decided to quash the semi-independence of Texas, having succeeded in doing so in Coahuila (in 1824, Mexico had merged Texas and Coahuila into the massive state of Coahuila y Tejas). Finally, Stephen F. Austin called Texians to arms; they declared independence from Mexico in 1836, and after Santa Anna defeated the Texians at the Alamo, he was defeated by the Texian Army commanded by General Sam Houston and captured at the Battle of San Jacinto and signed a treaty recognizing Texas' independence.
Texas consolidated its status as an independent republic and received official recognition from Britain, France, and the United States, which all advised Mexico not to try to reconquer the new nation. Most Texians wanted to join the United States but annexation of Texas was contentious in the U.S. Congress, where Whigs were largely opposed. In 1845 Texas agreed to the offer of annexation by the U.S. Congress. Texas became the 28th state on December 29, 1845.
Prelude to War
The border of Texas as an independent state was originally never settled. The Republic of Texas claimed land up to the Rio Grande based on the Treaties of Velasco, but Mexico refused to accept these as valid, claiming that the Rio Grande in the treaty was the Nueces, and referred to the Rio Grande as the Rio Bravo. Reference to the Rio Grande boundary of Texas was omitted from the U.S. Congress's annexation resolution to help secure passage after the annexation treaty failed in the Senate. President Polk claimed the Rio Grande boundary, and when Mexico sent forces over the Rio Grande, this rovoked a dispute.
In July 1845, Polk sent General Zachary Taylor to Texas, and by October 3,500 U.S. soldiers were on the Nueces River, ready to take by force the disputed land. Polk wanted to protect the border and also coveted for the U.S. the continent clear to the Pacific Ocean. At the same time Polk wrote to Thomas Larkin, the U.S. consul in the Mexican territory of Alta California, disclaiming U.S. ambitions in California, but offering to support independence from Mexico or voluntary accession to the U.S., and warning that the U.S. would oppose a British or French takeover.
To end another war scare with Great Britain over the Oregon Country, Polk signed the Oregon Treaty dividing the territory, angering northern Democrats who felt he was prioritizing Southern expansion over Northern expansion.
In the Winter of 1845–46, the federally commissioned explorer John C. Frémont and a group of armed men appeared in California. After telling the Mexican governor and the U.S. Consul Larkin he was merely buying supplies on the way to Oregon, he instead entered the populated area of California and visited Santa Cruz and the Salinas Valley, explaining he had been looking for a seaside home for his mother. Mexican authorities became alarmed and ordered him to leave. Frémont responded by building a fort on Gavilan Peak and raising the U.S. flag. Larkin sent word that Frémont's actions were counterproductive. Frémont left California in March but returned to California and assisted the Bear Flag Revolt in Sonoma, where many U.S. immigrants stated that they were playing "the Texas game" and declared California's independence from Mexico.
On November 10, 1845, Polk sent John Slidell, a secret representative, to Mexico City with an offer to the Mexican government of $25 million ($683,750,000 today) for the Rio Grande border in Texas and Mexico's provinces of Alta California and Santa Fe de Nuevo México. U.S. expansionists wanted California to thwart British ambitions in the area and to gain a port on the Pacific Ocean. Polk authorized Slidell to forgive the $3 million ($82 million today) owed to U.S. citizens for damages caused by the Mexican War of Independence and pay another $25 to $30 million ($684 million to $821 million today) in exchange for the two territories.
Mexico was not inclined nor able to negotiate. In 1846 alone, the presidency changed hands four times, the war ministry six times, and the finance ministry sixteen times. Mexican public opinion and all political factions agreed that selling the territories to the United States would tarnish the national honor. Mexicans who opposed direct conflict with the United States, including President José Joaquín de Herrera, were viewed as traitors. Military opponents of de Herrera, supported by populist newspapers, considered Slidell's presence in Mexico City an insult. When de Herrera considered receiving Slidell to settle the problem of Texas annexation peacefully, he was accused of treason and deposed. After a more nationalistic government under General Mariano Paredes y Arrillaga came to power, it publicly reaffirmed Mexico's claim to Texas; Slidell, convinced that Mexico should be "chastised", returned to the U.S.
Challenges in Mexico
The Mexican Army emerged from the war of independence (1810-1821) as a weak and divided force. Before the war with the United States, the military faced both internal and foreign challenges. The Spanish still occupied the coastal fortress or San Juan de Ulúa, and Spain did not recognize Mexico's independence, so that the new nation was at risk for invasion. In 1829, the Spanish attempted to reconquer their former colony and Antonio López de Santa Anna became a national hero defending the homeland. The army had a set of privileges (fueros), established in the colonial era, that gave it jurisdiction over many aspects of its affairs. In general, the military supported conservative positions, advocating a strong central government and upholding privileges of the military and the Catholic Church.
Some military men exercised power in local areas as caudillos and resisted central command. Liberal politicians, such as Valentín Gómez Farías, sought to rein in the military's power. The military faced insurrections and separatist movements in Tabasco, Yucatán, and Texas. The French blockaded in Veracruz in 1838 to collect debts, a conflict known to history as the Pastry War. Compounding the demands on the Mexican military, there were continuing Indian challenges to power in the northern region.
On the Mexican side, only 7 of the 19 states that formed the Mexican federation sent soldiers, armament, and money for the war effort, as the young Republic had not yet developed a sense of a unifying, national identity.
Mexican soldiers were not easily melded into an effective fighting force. Santa Anna said "the leaders of the army did their best to train the rough men who volunteered, but they could do little to inspire them with patriotism for the glorious country they were honored to serve." According to leading conservative politician Lucas Alamán, the "money spent on arming Mexican troops merely enabled them to fight each other and 'give the illusion' that the country possessed an army for its defense." However, an officer criticized Santa Anna's training of troops, "The cavalry was drilled only in regiments. The artillery hardly ever maneuvered and never fired a blank shot. The general in command was never present on the field of maneuvers, so that he was unable to appreciate the respective qualities of the various bodies under his command.... If any meetings of the principal commanding officers were held to discuss the operations of the campaign, it was not known, nor was it known whether any plan of campaign had been formed."
At the beginning of the war, Mexican forces were divided between the permanent forces (permanentes) and the active militiamen (activos). The permanent forces consisted of 12 regiments of infantry (of two battalions each), three brigades of artillery, eight regiments of cavalry, one separate squadron and a brigade of dragoons. The militia amounted to nine infantry and six cavalry regiments. In the northern territories of Mexico, presidial companies (presidiales) protected the scattered settlements there.
One of the contributing factors to loss of the war by Mexico was the inferiority of their weapons. The Mexican army was using British muskets (e.g. Brown Bess) from the Napoleonic Wars. In contrast to the aging Mexican standard-issue infantry weapon, some U.S. troops had the latest U.S.-manufactured breech-loading Hall rifles and Model 1841 percussion rifles. In the later stages of the war, U.S. cavalry and officers were issued Colt Walker revolvers, of which the U.S. Army had ordered 1,000 in 1846. Throughout the war, the superiority of the U.S. artillery often carried the day.
Desertion was a major problem for the Mexican army, depleting forces on the eve of battle. Most soldiers were peasants who had a loyalty to their village and family, but not to the generals who had conscripted them. Often hungry and ill, under-equipped, only partially trained, and never well paid, the soldiers were held in contempt by their officers and had little reason to fight the invading U.S. forces. Looking for their opportunity, many slipped away from camp to find their way back to their home village.
Political divisions inside Mexico were another factor in the U.S. victory. Inside Mexico, the centralistas and republicanos vied for power, and at times these two factions inside Mexico's military fought each other rather than the invading U.S. Army. Another faction called the monarchists, whose members wanted to install a monarch (some even advocated rejoining Spain), further complicated matters. This third faction would rise to predominance in the period of the French intervention in Mexico. The ease of the American landing at Vera Cruz was in large part due to civil warfare in Mexico City, which made any real defense of the port city impossible. As Gen. Santa Anna said, "However shameful it may be to admit this, we have brought this disgraceful tragedy upon ourselves through our interminable in-fighting."
United States Combatants
On the United States side, the war was fought by regiments of regulars and various regiments, battalions, and companies of volunteers from the different states of the Union and the Americans and some of the Mexicans in the territory of California and New Mexico. On the West Coast, the U.S. Navy fielded a battalion of sailors, in an attempt to recapture Los Angeles. Although the U.S. Army and Navy were not large at the outbreak of the war, the officers were generally well trained and the numbers of enlisted men fairly large compared to Mexico's. At the beginning of the war, the U.S. Army had eight regiments of infantry (three battalions each), four artillery regiments and three mounted regiments (two dragoons, one of mounted rifles). These regiments were supplemented by 10 new regiments (nine of infantry and one of cavalry) raised for one year of service by the act of Congress from February 11, 1847.
State volunteers were raised in various sized units and for various periods of time, mostly for one year. Later some were raised for the duration of the war as it became clear it was going to last longer than a year.
U.S. soldiers' memoirs describe cases of looting and murder of Mexican civilians, mostly by State Volunteers. One officer's diary records:
We reached Burrita about 5 pm, many of the Louisiana volunteers were there, a lawless drunken rabble. They had driven away the inhabitants, taken possession of their houses, and were emulating each other in making beasts of themselves.
John L. O'Sullivan, a vocal proponent of Manifest Destiny, later recalled:
The regulars regarded the volunteers with importance and contempt ... [The volunteers] robbed Mexicans of their cattle and corn, stole their fences for firewood, got drunk, and killed several inoffensive inhabitants of the town in the streets.
Many of the volunteers were unwanted and considered poor soldiers. The expression "Just like Gaines's army" came to refer to something useless, the phrase having originated when a group of untrained and unwilling Louisiana troops were rejected and sent back by Gen. Taylor at the beginning of the war.
Outbreak of the War
Initial Skirmish at the Nueces Strip
President James K. Polk ordered General Taylor and his forces south to the Rio Grande, entering the territory that Mexicans disputed. Mexico laid claim to all the lands as far north as the Nueces River—about 150 mi (240 km) north of the Rio Grande. The U.S. claimed that the border was the Rio Grande, citing the 1836 Treaties of Velasco. Mexico rejected the treaties and refused to negotiate; it claimed all of Texas. Taylor ignored Mexican demands to withdraw to the Nueces. He constructed a makeshift fort (later known as Fort Brown/Fort Texas) on the banks of the Rio Grande opposite the city of Matamoros, Tamaulipas.
Mexican forces under General Mariano Arista prepared for war. On April 25, 1846, a 2,000-strong Mexican cavalry detachment attacked a 70-man U.S. patrol under the command of Captain Seth Thornton, which had been sent into the contested territory north of the Rio Grande and south of the Nueces River. In the Thornton Affair, the Mexican cavalry routed the patrol, killing 16 American soldiers.
A few days after the defeat of the U.S. troops by General Arista, the Siege of Fort Texas began on May 3, 1846. Mexican artillery at Matamoros opened fire on Fort Texas, which replied with its own guns. The bombardment continued for 160 hours and expanded as Mexican forces gradually surrounded the fort. Thirteen U.S. soldiers were injured during the bombardment, and two were killed. Among the dead was Jacob Brown, after whom the fort was later named.
On May 8, Zachary Taylor and 2,400 troops arrived to relieve the fort. However,General Arista rushed north and intercepted him with a force of 3,400 at Palo Alto. The U.S. Army employed "flying artillery", their term for horse artillery, a type of mobile light artillery that was mounted on horse carriages with the entire crew riding horses into battle. It had a devastating effect on the Mexican army. In contrast to the "flying artillery" of the Americans, the Mexican cannons at the Battle of Palo Alto fired at such slow velocities that it was possible for American soldiers to dodge artillery rounds. The Mexicans replied with cavalry skirmishes and their own artillery. The U.S. flying artillery somewhat demoralized the Mexican side, and seeking terrain more to their advantage, the Mexicans retreated to the far side of a dry riverbed (resaca) during the night. It provided a natural fortification, but during the retreat, Mexican troops were scattered, making communication difficult.
During the Battle of Resaca de la Palma the next day, the two sides engaged in fierce hand to hand combat. The U.S. Cavalry managed to capture the Mexican artillery, causing the Mexican side to retreat—a retreat that turned into a rout. Fighting on unfamiliar terrain, his troops fleeing in retreat, Arista found it impossible to rally his forces. Mexican casualties were heavy, and the Mexicans were forced to abandon their artillery and baggage. Fort Brown inflicted additional casualties as the withdrawing troops passed by the fort. Many Mexican soldiers drowned trying to swim across the Rio Grande. Both these engagements were fought prior to war being declared.
Declarations of war
In 1846, relations between the two countries had deteriorated considerably and on April 23, 1846, the president of Mexico issued a proclamation, declaring Mexico's intent to fight a "defensive war" against the encroachment of the United States. On April 25, 1846, 2,000 Mexican cavalry crossed into the disputed territory and routed a small detachment of American soldiers sparking the "Thornton Affair"  Polk received word of the Thornton Affair, which, added to the Mexican government's rejection of Slidell, Polk believed, constituted a casus belli (cause for war). His message to Congress on May 11, 1846, claimed that "Mexico has passed the boundary of the United States, has invaded our territory and shed American blood upon American soil."
The U.S. Congress approved the declaration of war on May 13, 1846, after a few hours of debate, with southern Democrats in strong support. Sixty-seven Whigs voted against the war on a key slavery amendment, but on the final passage only 14 Whigs voted no, including Rep. John Quincy Adams.
In Mexico, although President Paredes issued a manifesto on May 23, 1846 and a declaration of a defensive war on April 23, both of which are considered by some the de facto start of the war, Mexico officially declared war by Congress on July 7, 1846.
Antonio López de Santa Anna
Once the U.S. declared war on Mexico, Antonio López de Santa Anna wrote to the Mexican government, saying he no longer had aspirations to the presidency, but would eagerly use his military experience to fight off the foreign invasion of Mexico as he had before. President Valentín Gómez Farías, a civilian, was desperate enough to accept the offer and allowed Santa Anna to return. Meanwhile, Santa Anna had secretly been dealing with representatives of the U.S., pledging that if he were allowed back in Mexico through the U.S. naval blockades he would work to sell all contested territory to the United States at a reasonable price. Once back in Mexico at the head of an army, Santa Anna reneged on both agreements. He declared himself president once again and unsuccessfully tried to fight off the U.S. invasion.
Reaction in the U.S.
Opposition to the war
In the U.S., increasingly divided by sectional rivalry, the war was a partisan issue and an essential element in the origins of the American Civil War. Most Whigs in the North and South opposed it; most Democrats supported it. Southern Democrats, animated by a popular belief in Manifest Destiny, supported it in hope of adding slave-owning territory to the South and avoiding being outnumbered by the faster-growing North. John L. O'Sullivan, editor of the Democratic Review, coined this phrase in its context, stating that it must be "our manifest destiny to overspread the continent allotted by Providence for the free development of our yearly multiplying millions."
Northern antislavery elements feared the expansion of the Southern Slave Power; Whigs generally wanted to strengthen the economy with industrialization, not expand it with more land. Among the most vocal opposing the war in the House of Representatives was John Quincy Adams of Massachusetts. Adams had first voiced concerns about expanding into Mexican territory in 1836 when he opposed Texas annexation. He continued this argument in 1846 for the same reason. War with Mexico would add new slavery territory to the nation. When the vote to go to war with Mexico came to a vote on May 13, Adams spoke a resounding "NO" in the chamber. Only 13 others followed his lead.
Ex-slave Frederick Douglass opposed the war and was dismayed by the weakness of the anti-war movement. "The determination of our slave holding president, and the probability of his success in wringing from the people, men and money to carry it on, is made evident by the puny opposition arrayed against him. None seem willing to take their stand for peace at all risks."
Democrats wanted more land; northern Democrats were attracted by the possibilities in the far northwest. Joshua Giddings led a group of dissenters in Washington D.C. He called the war with Mexico "an aggressive, unholy, and unjust war", and voted against supplying soldiers and weapons. He said:
In the murder of Mexicans upon their own soil, or in robbing them of their country, I can take no part either now or hereafter. The guilt of these crimes must rest on others. I will not participate in them.
Fellow Whig Abraham Lincoln contested the causes for the war and demanded to know exactly where Thornton had been attacked and American blood shed. "Show me the spot", he demanded. Whig leader Robert Toombs of Georgia declared:
This war is nondescript.... We charge the President with usurping the war-making power ... with seizing a country ... which had been for centuries, and was then in the possession of the Mexicans.... Let us put a check upon this lust of dominion. We had territory enough, Heaven knew.
Northern abolitionists attacked the war as an attempt by slave-owners to strengthen the grip of slavery and thus ensure their continued influence in the federal government. Acting on his convictions, Henry David Thoreau was jailed for his refusal to pay taxes to support the war, and penned his famous essay Civil Disobedience.
Democratic Congressman David Wilmot introduced the Wilmot Proviso, which aimed to prohibit slavery in new territory acquired from Mexico. Wilmot's proposal did not pass Congress, but it spurred further hostility between the factions.
Defense of the war in the U.S.
Besides alleging that the actions of Mexican military forces within the disputed boundary lands north of the Rio Grande constituted an attack on American soil, the war's advocates viewed the territories of New Mexico and California as only nominally Mexican possessions with very tenuous ties to Mexico. They saw the territories as actually unsettled, ungoverned, and unprotected frontier lands, whose non-aboriginal population, where there was any at all, represented a substantial—in places even a majority—Anglo American component. Moreover, the territories were feared to be under imminent threat of acquisition by the U.S. rival on the continent, Great Britain.
President Polk reprised these arguments in his Third Annual Message to Congress on December 7, 1847. In it he scrupulously detailed his administration's position on the origins of the conflict, the measures the U.S. had taken to avoid hostilities, and the justification for declaring war. He also elaborated upon the many outstanding financial claims by U.S. citizens against Mexico and argued that, in view of the country's insolvency, the cession of some large portion of its northern territories was the only indemnity realistically available as compensation. This helped to rally congressional Democrats to his side, ensuring passage of his war measures and bolstering support for the war in the U.S.
U.S. press and popular war enthusiasm
Whipping up support for the war was embraced by the press. Richard Caton Woodville's lithograph, War News From Mexico satirizes the reactions of various segments of the American population to the war. The lithograph is generally considered unfavorable to the war's apparent pro-slavery motivations. 
The coverage of the war was an important development in the U.S., with journalists as well as letter-writing soldiers gave the public in the U.S. "their first-ever independent news coverage of warfare from home or abroad." During the war, inventions such as the telegraph created new means of communication that updated people with the latest news from the reporters, who were on the scene. The most important of these was George Wilkins Kendall, a Northerner who wrote for the New Orleans Picayune, and whose collected Dispatches from the Mexican War constitute an important primary source for the conflict. With more than a decade's experience reporting urban crime, the "penny press" realized the public's voracious demand for astounding war news. Moreover, Shelley Streetby demonstrates that the print revolution (1830s-1840s), which preceded the U.S.-Mexican War, made it possible for the distribution of cheap newspapers throughout the country. This was the first time in U.S. history that accounts by journalists, instead of opinions of politicians, had great influence in shaping people's opinions about and attitudes toward a war. Along with written accounts of the war, there were war artists giving a visual dimension to the war at the time and immediately afterward. Carl Nebel's visual depictions of the war are well known.
By getting constant reports from the battlefield, many in the U.S. became emotionally united as a community. News about the war always caused extraordinary popular excitement. In the Spring of 1846, news about Zachary Taylor's victory at Palo Alto brought up a large crowd that met in a cotton textile town of Lowell, Massachusetts. New York celebrated the twin victories at Veracruz and Buena Vista in May 1847. Among fireworks and illuminations, they had a "grand procession" of about 400,000 people. Generals Taylor and Scott became heroes for their people and later became presidential candidates.
Conduct of the war
After the declaration of war on May 13, 1846, U.S. forces invaded Mexican territory on two main fronts. The U.S. War Department sent a U.S. Cavalry force under Stephen W. Kearny to invade western Mexico from Jefferson Barracks and Fort Leavenworth, reinforced by a Pacific fleet under John D. Sloat. This was done primarily because of concerns that Britain might also try to seize the area. Two more forces, one under John E. Wool and the other under Taylor, were ordered to occupy Mexico as far south as the city of Monterrey.
New Mexico Campaign
United States Army General Stephen W. Kearny moved southwest from Fort Leavenworth, Kansas with about 1,700 men in his Army of the West. Kearny's orders were to secure the territories Nuevo México and Alta California.
In Santa Fe, Governor Manuel Armijo wanted to avoid battle, but on August 9, Catholic priests, Diego Archuleta (the young regular-army commander), and the young militia officers Manuel Chaves and Miguel Pino forced him to muster a defense. Armijo set up a position in Apache Canyon, a narrow pass about 10 miles (16 km) southeast of the city. However, on August 14, before the American army was even in view, he decided not to fight. (An American named James Magoffin claimed he had convinced Armijo and Archuleta to follow this course; an unverified story says he bribed Armijo.) When Pino, Chaves, and some of the militiamen insisted on fighting, Armijo ordered the cannon pointed at them. The New Mexican army retreated to Santa Fe, and Armijo fled to Chihuahua.
Kearny and his troops encountered no Mexican forces when they arrived on August 15. Kearny and his force entered Santa Fe and claimed the New Mexico Territory for the United States without a shot being fired. Kearny declared himself the military governor of the New Mexico Territory on August 18 and established a civilian government. He then took the remainder of his army west to Alta California.
Following Kearny's departure, dissenters in Santa Fe plotted a Christmas uprising. When the plans were discovered by the US authorities, the dissenters postponed the uprising. They attracted numerous Indian allies, including Puebloan peoples, who also wanted to push the Americans from the territory. On the morning of January 19, 1847, the insurrectionists began the revolt in Don Fernando de Taos, present-day Taos, New Mexico, which later gave it the name the Taos Revolt. They were led by Pablo Montoya, a New Mexican, and Tomás Romero, a Taos pueblo Indian also known as Tomasito (Little Thomas).
Romero led an Indian force to the house of Governor Charles Bent, where they broke down the door, shot Bent with arrows, and scalped him in front of his family. They moved on, leaving Bent still alive. With his wife Ignacia and children, and the wives of friends Kit Carson and Thomas Boggs, the group escaped by digging through the adobe walls of their house into the one next door. When the insurgents discovered the party, they killed Bent, but left the women and children unharmed.
The next day a large armed force of approximately 500 New Mexicans and Pueblo attacked and laid siege to Simeon Turley's mill in Arroyo Hondo, several miles outside of Taos. Charles Autobees, an employee at the mill, saw the men coming. He rode to Santa Fe for help from the occupying US forces. Eight to ten mountain men were left at the mill for defense. After a day-long battle, only two of the mountain men, John David Albert and Thomas Tate Tobin, Autobees' half brother, survived. Both escaped separately on foot during the night. The same day New Mexican insurgents killed seven American traders who were passing through the village of Mora. At most, 15 of the U.S. forces were killed in both actions on January 20.
The US military moved quickly to quash the revolt; Col. Price led more than 300 U.S. troops from Santa Fe to Taos, together with 65 volunteers, including a few New Mexicans, organized by Ceran St. Vrain, the business partner of the brothers William and Charles Bent. Along the way, the combined forces beat back a force of some 1,500 New Mexicans and Pueblo at Santa Cruz de la Cañada and Embudo Pass. The insurgents retreated to Taos Pueblo, where they took refuge in the thick-walled adobe church.
During the ensuing battle, the US breached a wall of the church and directed cannon fire into the interior, inflicting many casualties and killing about 150 rebels. They captured 400 more men after close hand-to-hand fighting. Only seven Americans died in the battle.
A separate force of US troops under captains Israel R. Hendley and Jesse I. Morin campaigned against the rebels in Mora. The First Battle of Mora ended in a New Mexican victory. The Americans attacked again in the Second Battle of Mora and won, which ended their operations against Mora. New Mexican rebels engaged US forces three more times in the following months. The actions are known as the Battle of Red River Canyon, the Battle of Las Vegas, and the Battle of Cienega Creek. After the U.S. forces won each battle, the New Mexicans and Indians ended open warfare.
Although the U.S. declared war against Mexico on May 13, 1846, it took almost three months (until early August 1846) for definitive word of Congress' declaration of war to get to California. U.S. consul Thomas O. Larkin, stationed in Monterey, worked successfully during the events in that vicinity to avoid bloodshed between Anglo Americans and the Mexican military garrison commanded by General José Castro, the senior military officer in California.
Captain John C. Frémont, leading a U.S. Army topographical expedition to survey the Great Basin, entered the Sacramento Valley in December 1845. Frémont's party was at Upper Klamath Lake, Oregon Territory, when it received word that war between Mexico and the U.S. was imminent; the party then returned to California.
Mexico had issued a proclamation that unnaturalized foreigners were no longer permitted to have land in California and were subject to expulsion. With rumors swirling that General Castro was massing an army against them, American settlers in the Sacramento Valley banded together to meet the threat. On June 14, 1846, 34 American settlers seized control of the undefended Mexican government outpost of Sonoma to forestall Castro's plans. One settler created the Bear Flag and raised it over Sonoma Plaza. Within a week, 70 more volunteers joined the rebels' force, which grew to nearly 300 in early July. This event, led by William B. Ide, became known as the Bear Flag Revolt.
On June 25, Frémont's party arrived to assist in an expected military confrontation. San Francisco, then called Yerba Buena, was occupied by the Bear Flaggers on July 2. On July 5 Frémont's California Battalion was formed by combining his forces with many of the rebels.
Commodore John D. Sloat, commander of the U.S. Navy's Pacific Squadron, near Mazatlan, Mexico, had received orders to seize San Francisco Bay and blockade California ports when he was positive that war had begun. Sloat set sail for Monterey, reaching it on July 1. Sloat, upon hearing of the events in Sonoma and Frémont's involvement, erroneously believed Frémont to be acting on orders from Washington and ordered his forces to occupy Monterey on July 7 and raise the U.S. flag.
On Sloat's orders, Frémont brought 160 volunteers to Monterey, in addition to the California Battalion. On July 15, Sloat transferred his command of the Pacific Squadron to Commodore Robert F. Stockton, who was more militarily aggressive. He mustered the willing members of the California Battalion into military service with Frémont in command. Stockton ordered Frémont to San Diego to prepare to move northward to Los Angeles. As Frémont landed, Stockton's 360 men arrived in San Pedro. General Castro and Governor Pío Pico wrote farewells and left separately to the Mexican state of Sonora.
Stockton's army entered Los Angeles unopposed on August 13, whereupon he sent a report to the Secretary of State that "California is entirely free from Mexican dominion." Stockton, however, left a tyrannical officer in charge of Los Angeles with a small force. The Californios under the leadership of José María Flores, acting on their own and without federal help from Mexico, in the Siege of Los Angeles, forced the U.S. garrison to retreat on September 29. They also forced small U.S. garrisons in San Diego and Santa Barbara to flee.
Captain William Mervine landed 350 sailors and marines at San Pedro on October 7. They were ambushed and repulsed at the Battle of Dominguez Rancho by Flores' forces in less than an hour. Four U.S. nationals died, with 8 severely injured. Stockton arrived with reinforcements at San Pedro, which increased the U.S. forces there to 800. He and Mervine then set up a base of operations at San Diego.
Meanwhile, U.S. Colonel Stephen W. Kearny and his force of about 100 men, who had performed a grueling march across New Mexico and the Sonoran Desert, crossed the Colorado River in late November, 1846. Stockton sent a 35-man patrol from San Diego to meet them. On December 7, 100 lancers under General Andrés Pico (brother of the governor), tipped off and lying in wait, fought Kearny's army of about 150 at the Battle of San Pasqual, where 22 of Kearny's men (one of whom later died of wounds), including three officers, were killed in 30 minutes of fighting. The wounded Kearny and his bloodied force pushed on until they had to establish a defensive position on "Mule Hill". However, General Pico kept the hill under siege for four days until a 215-man U.S. relief force arrived.
Frémont and the 428-man California Battalion arrived in San Luis Obispo on December 14 and Santa Barbara on December 27. On December 28, a 600-man U.S. force under Kearny began a 150-mile march to Los Angeles. Flores then moved his ill-equipped 500-man force to a 50-foot-high bluff above the San Gabriel River. On January 8, 1847, the Stockton-Kearny army defeated the Californio force in the two-hour Battle of Rio San Gabriel. That same day, Frémont's force arrived at San Fernando. The next day, January 9, the Stockton-Kearny forces fought and won the Battle of La Mesa. On January 10, the U.S. Army entered Los Angeles to no resistance.
On January 12, Frémont and two of Pico's officers agreed to terms for a surrender. Articles of Capitulation were signed on January 13 by Frémont, Andrés Pico and six others at a rancho at Cahuenga Pass (modern-day North Hollywood). This became known as the Treaty of Cahuenga, which marked the end of armed resistance in California.
Pacific Coast campaign
USS Independence assisted in the blockade of the Mexican Pacific coast, capturing the Mexican ship Correo and a launch on May 16, 1847. She supported the capture of Guaymas, Sonora, on October 19, 1847, and landed bluejackets and Marines to occupy Mazatlán, Sinaloa, on November 11, 1847. After upper California was secure, most of the Pacific Squadron proceeded down the California coast, capturing all major cities of the Baja California Territory and capturing or destroying nearly all Mexican vessels in the Gulf of California. Other ports, not on the peninsula, were taken as well. The objective of the Pacific Coast Campaign was to capture Mazatlán, on the Mexican mainland, which was a major supply base for Mexican forces. Numerous Mexican ships were also captured by this squadron, with the USS Cyane given credit for 18 ships captured and numerous destroyed.
Entering the Gulf of California, Independence, Congress, and Cyane seized La Paz, then captured and burned the small Mexican fleet at Guaymas. Within a month, they cleared the Gulf of Mexican ships, destroying or capturing 30 vessels. Later, their sailors and marines captured the port of Mazatlán on November 11, 1847. A Mexican campaign under Manuel Pineda Muñoz to retake the various captured ports resulted in several small clashes (Battle of Mulege, Battle of La Paz, Battle of San José del Cabo) and two sieges (Siege of La Paz, Siege of San José del Cabo) in which the Pacific Squadron ships provided artillery support. U.S. garrisons remained in control of the ports.
Following reinforcement, Lt. Col. Henry S. Burton marched out. His forces rescued captured U.S. nationals, captured Pineda, and, on March 31, defeated and dispersed remaining Mexican forces at the Skirmish of Todos Santos, unaware that the Treaty of Guadalupe Hidalgo had been signed in February 1848 and a truce agreed to on March 6. When the U.S. garrisons were evacuated to Monterey following the treaty ratification, many Mexicans went with them: those who had supported the U.S. cause and had thought Lower California would also be annexed along with Upper California.
The Mexican Army's defeats at Palo Alto and Resaca de la Palma caused political turmoil in Mexico, turmoil which Antonio López de Santa Anna used to revive his political career and return from self-imposed exile in Cuba in mid-August 1846. It was President Polk's plan to bring back the exiled dictator who had defeated the Texans at the Alamo and Goliad. On 4 August 1846, "Polk negotiated a deal to not only bring Santa Anna back, but to pay him $2 million—ostensibly a bribe as an advance payment on the cession of California."
Santa Anna promised the U.S. that if allowed to pass through the blockade, he would negotiate a peaceful conclusion to the war and sell the New Mexico and Alta California territories to the U.S. Once Santa Anna arrived in Mexico City, however, he reneged on his deal with the U.S. and offered his services to the Mexican government. Then, after being appointed commanding general, he reneged again and seized the presidency.
Led by Zachary Taylor, 2,300 U.S. troops crossed the Rio Grande after some initial difficulties in obtaining river transport. His soldiers occupied the city of Matamoros, then Camargo (where the soldiery suffered the first of many problems with disease) and then proceeded south and besieged the city of Monterrey. The hard-fought Battle of Monterrey resulted in serious losses on both sides. The U.S. Army's light artillery was ineffective against the stone fortifications of the city. The Mexican forces were under General Pedro de Ampudia and repulsed Taylor's best infantry division at Fort Teneria.
U.S. Army soldiers, including many West Pointers, had never engaged in urban warfare before and they marched straight down the open streets, where they were annihilated by Mexican defenders well-hidden in Monterrey's thick adobe homes. Two days later, they changed their urban warfare tactics. Texan soldiers had fought in a Mexican city before (the Siege of Béxar in December 1835) and advised Taylor's generals that the U.S. forces needed to "mouse hole" through the city's homes. In other words, they needed to punch holes in the side or roofs of the homes and fight hand to hand inside the structures. Mexicans called the Texas soldiers the Diabólicos Tejanos (the Devil Texans). This method proved successful. Eventually, these actions drove and trapped Ampudia's men into the city's central plaza, where howitzer shelling forced Ampudia to negotiate. Taylor agreed to allow the Mexican Army to evacuate and to an eight-week armistice in return for the surrender of the city. Under pressure from Washington, Taylor broke the armistice and occupied the city of Saltillo, southwest of Monterrey. Santa Anna blamed the loss of Monterrey and Saltillo on Ampudia and demoted him to command a small artillery battalion.
On February 22, 1847, Santa Anna personally marched north to fight Taylor with 20,000 men. Taylor, with 4,600 men, had entrenched at a mountain pass called Buena Vista. Santa Anna suffered desertions on the way north and arrived with 15,000 men in a tired state. He demanded and was refused surrender of the U.S. Army; he attacked the next morning. Santa Anna flanked the U.S. positions by sending his cavalry and some of his infantry up the steep terrain that made up one side of the pass, while a division of infantry attacked frontally along the road leading to Buena Vista. Furious fighting ensued, during which the U.S troops were nearly routed, but managed to cling to their entrenched position, thanks to the Mississippi Rifles, a volunteer regiment led by Jefferson Davis, who formed them into a defensive V formation. The Mexicans had inflicted considerable losses but Santa Anna had gotten word of upheaval in Mexico City, so he withdrew that night, leaving Taylor in control of part of Northern Mexico.
Polk mistrusted Taylor, whom he felt had shown incompetence in the Battle of Monterrey by agreeing to the armistice, and may have considered him a political rival for the White House. Taylor later used the Battle of Buena Vista as the centerpiece of his successful 1848 presidential campaign.
Although the war is generally characterized as being between two sovereign nations, Indian groups were also involved in the conflict and had an impact. The non-Indian civilian population of northern Mexico offered little resistance to the U.S. invasion, possibly because the country had already been devastated by Comanche and Apache Indian raids. Josiah Gregg, who was with the U.S. Army in northern Mexico, said that "the whole country from New Mexico to the borders of Durango is almost entirely depopulated. The haciendas and ranchos have been mostly abandoned, and the people chiefly confined to the towns and cities."
The Treaty of Bear Springs ended a large scale insurrection by the Ute, Zuni, Moquis, and Navajo tribes. After the successful conquest of New Mexico, U.S. troops moved into modern-day northwest Mexico.
On March 1, 1847, Alexander W. Doniphan occupied Chihuahua City. British consul John Potts did not want to let Doniphan search Governor Trias's mansion, and unsuccessfully asserted it was under British protection. American merchants in Chihuahua wanted the American force to stay in order to protect their business. Major William Gilpin advocated a march on Mexico City and convinced a majority of officers, but Doniphan subverted this plan. Then in late April, Taylor ordered the First Missouri Mounted Volunteers to leave Chihuahua and join him at Saltillo. The merchants who were U.S. nationals either followed or returned to Santa Fe. Along the way, the townspeople of Parras enlisted Doniphan's aid against an Indian raiding party that had taken children, horses, mules, and money.
First Battle of Tabasco
Commodore Matthew C. Perry led a detachment of seven vessels along the southern coast of Tabasco state. Perry arrived at the Tabasco River (now known as the Grijalva River) on October 22, 1846, and seized the town Port of Frontera along with two of their ships. Leaving a small garrison, he advanced with his troops towards the town of San Juan Bautista (Villahermosa today). Perry arrived in the city of San Juan Bautista on October 25, seizing five Mexican vessels. Colonel Juan Bautista Traconis, Tabasco Departmental commander at that time, set up barricades inside the buildings. Perry realized that the bombing of the city would be the only option to drive out the Mexican Army, and avoiding damage to the merchants of the city, withdrew its forces preparing them for the next day.
On the morning of October 26, as Perry's fleet prepared to start the attack on the city, the Mexican forces began firing at the American fleet. The U.S. bombing began to yield the square, so that the fire continued until evening. Before taking the square, Perry decided to leave and return to the port of Frontera, where he established a naval blockade to prevent supplies of food and military supplies from reaching the state capital.
Second Battle of Tabasco
On June 13, 1847, Commodore Perry assembled the Mosquito Fleet and began moving towards the Grijalva River, towing 47 boats that carried a landing force of 1,173. On June 15, 12 miles (19 km) below San Juan Bautista, the fleet ran through an ambush with little difficulty. Again at an "S" curve in the river known as the "Devil's Bend", Perry encountered Mexican fire from a river fortification known as the Colmena redoubt, but the fleet's heavy naval guns quickly dispersed the Mexican force.
On June 16, Perry arrived at San Juan Bautista and commenced bombing the city. The attack included two ships that sailed past the fort and began shelling it from the rear. David D. Porter led 60 sailors ashore and seized the fort, raising the U.S. flag over the works. Perry and the landing force arrived and took control of the city around 14:00.
Desertion from U.S. Army
The desertion rate in the U.S. Army was 8.3% (9,200 out of 111,000), compared to 12.7% during the War of 1812 and usual peacetime rates of about 14.8% per year. Many men deserted to join another U.S. unit and get a second enlistment bonus. Some deserted because of the miserable conditions in camp. It has been suggested that others used the army to get free transportation to California, where they deserted to join the gold rush; this, however, is unlikely as gold was only discovered in California on January 24, 1848, less than two weeks before the war concluded. By the time word reached the eastern U.S. that gold had been discovered, word also reached it that the war was over.
Several hundred U.S. deserters went over to the Mexican side. Nearly all were recent immigrants from Europe with weak ties to the U.S.; the most famous group was the Saint Patrick's Battalion composed primarily of Catholic Irish and German immigrants, the battalion also included Canadians, English, French, Italians, Poles, Scots, Spaniards, Swiss, and Mexican people, many of whom were members of the Catholic Church. The Mexicans issued broadsides and leaflets enticing U.S. soldiers with promises of money, land bounties, and officers' commissions. Mexican guerrillas shadowed the U.S. Army and captured men who took unauthorized leave or fell out of the ranks. The guerrillas coerced these men to join the Mexican ranks. The generous promises proved illusory for most deserters, who risked being executed if captured by U.S. forces. About 50 of the San Patricios were tried and hanged following their capture at Churubusco in August 1847.
Scott's Mexico City campaign
Landings and Siege of Veracruz
Rather than reinforce Taylor's army for a continued advance, President Polk sent a second army under General Winfield Scott, which was transported to the port of Veracruz by sea, to begin an invasion of the Mexican heartland. On March 9, 1847, Scott performed the first major amphibious landing in U.S. history in preparation for the Siege of Veracruz. A group of 12,000 volunteer and regular soldiers successfully offloaded supplies, weapons, and horses near the walled city using specially designed landing craft. Included in the invading force were Robert E. Lee, George Meade, Ulysses S. Grant, James Longstreet, and Thomas "Stonewall" Jackson.
The city was defended by Mexican General Juan Morales with 3,400 men. Mortars and naval guns under Commodore Matthew C. Perry were used to reduce the city walls and harass defenders. After a bombardment on March 24, 1847, the walls of Veracruz had a thirty-foot gap. The city replied the best it could with its own artillery. The effect of the extended barrage destroyed the will of the Mexican side to fight against a numerically superior force, and they surrendered the city after 12 days under siege. U.S. troops suffered 80 casualties, while the Mexican side had around 180 killed and wounded, about half of whom were civilian. During the siege, the U.S. side began to fall victim to yellow fever.
Advance on Puebla
Scott then marched westward toward Mexico City with 8,500 healthy troops, while Santa Anna set up a defensive position in a canyon around the main road at the halfway mark to Mexico City, near the hamlet of Cerro Gordo. Santa Anna had entrenched with 12,000 troops and artillery that were trained on the road, along which he expected Scott to appear. However, Scott had sent 2,600 mounted dragoons ahead; the Mexican artillery prematurely fired on them and therefore revealed their positions.
Instead of taking the main road, Scott's troops trekked through the rough terrain to the north, setting up his artillery on the high ground and quietly flanking the Mexicans. Although by then aware of the positions of U.S. troops, Santa Anna and his troops were unprepared for the onslaught that followed. The Mexican army was routed. The U.S. Army suffered 400 casualties, while the Mexicans suffered over 1,000 casualties and 3,000 were taken prisoner. In August 1847, Captain Kirby Smith, of Scott's 3rd Infantry, reflected on the resistance of the Mexican army:
They can do nothing and their continued defeats should convince them of it. They have lost six great battles; we have captured six hundred and eight cannon, nearly one hundred thousand stands of arms, made twenty thousand prisoners, have the greatest portion of their country and are fast advancing on their Capital which must be ours,—yet they refuse to treat [i.e., negotiate terms]!
Pause at Puebla
In May, Scott pushed on to Puebla, the second largest city in Mexico. Because of the citizens' hostility to Santa Anna, the city capitulated without resistance on May 1. During the following months Scott gathered supplies and reinforcements at Puebla and sent back units whose enlistments had expired. Scott also made strong efforts to keep his troops disciplined and treat the Mexican people under occupation justly, so as to prevent a popular rising against his army.
Advance on Mexico City and its capture
With guerrillas harassing his line of communications back to Veracruz, Scott decided not to weaken his army to defend Puebla but, leaving only a garrison at Puebla to protect the sick and injured recovering there, advanced on Mexico City on August 7 with his remaining force. The capital was laid open in a series of battles around the right flank of the city defenses, at the Battle of Contreras and Churubusco, culminating in the Battle of Chapultepec. Fighting halted for a time when an armistice and peace negotiations followed the Battle of Churubusco, until they broke down, on September 6, 1847. With the subsequent battles of Molino del Rey and of Chapultepec, and the storming of the city gates, the capital was occupied. Winfield Scott became an American national hero after his victories in this campaign of the Mexican–American War, and later became military governor of occupied Mexico City.
Battle of Chapultepec
The Battle of Chapultepec was an encounter between the Mexican Army and the United States on the castle of Chapultepec in Mexico City. At this time, this castle was a renowned military school in Mexico City. After the battle, which ended in an American victory, the legend of "Los Niños Héroes" was born. Although not confirmed by historians, six military cadets between the ages of 13 and 17 stayed in the school instead of evacuating. They decided to stay and fight for Mexico. These Niños Héroes (hero children) became icons in Mexico's pantheon of heroes. Rather than surrender to the U.S. Army, some military cadets leaped from the castle walls. A cadet named Juan Escutia wrapped himself in the Mexican flag and jumped to his death.
Saint Patrick's Battalion (San Patricios) was a group of several hundred immigrant soldiers, the majority Irish, who deserted the U.S. Army because of ill-treatment or sympathetic leanings to fellow Mexican Catholics. They joined the Mexican army. Most were killed in the Battle of Churubusco; about 100 were captured by the U.S. and roughly ½ were hanged as deserters. The leader, Jon Riley, was merely branded since he had deserted prior to the start of the war.
Santa Anna's last campaign
In late September 1847, Santa Anna made one last attempt to defeat the Americans, by cutting them off from the coast. General Joaquín Rea began the Siege of Puebla, soon joined by Santa Anna, but they failed to take it before the approach of a relief column from Veracruz under Brig. Gen. Joseph Lane prompted Santa Anna to stop him. Puebla was relieved by Gen. Lane October 12, 1847, following his defeat of Santa Anna at the Battle of Huamantla on October 9, 1847. The battle was Santa Anna's last. Following the defeat, the new Mexican government led by Manuel de la Peña y Peña asked Santa Anna to turn over command of the army to General José Joaquín de Herrera.
Mexican guerrilla campaign
Following his capture and securing of the capital, General Scott sent about a quarter of his strength to secure his line of communications to Vera Cruz from the Light Corps of General Joaquín Rea and other Mexican guerrilla forces that had been harassing it since May. He strengthened the garrison of Puebla and by November had added a 1200-man garrison at Jalapa, established 750-man posts along the National Road, the main route between the port of Veracruz and the capital, at the pass between Mexico City and Puebla at Rio Frio, at Perote and San Juan on the road between Jalapa and Puebla and at Puente Nacional between Jalapa and Vera Cruz. He had also detailed an anti guerrilla brigade under Brig. Gen. Joseph Lane to carry the war to the Light Corps and other guerrillas. He ordered that convoys would travel with at least 1,300-man escorts. Victories by General Lane over the Light Corps at Atlixco (October 18, 1847), at Izucar de Matamoros (November 23, 1847) and Galaxara Pass (November 24, 1847) ended the threat of General Rea.
Later a raid against the guerrillas of Padre Jarauta at Zacualtipan (February 25, 1848), further reduced guerrilla raids on the U.S. line of communications. After the two governments concluded a truce to await ratification of the peace treaty, on March 6, 1848, formal hostilities ceased. However some bands continued in defiance of the Mexican government until the U.S. evacuation in August. Some were suppressed by the Mexican Army or, like Padre Jarauta, executed.
Treaty of Guadalupe Hidalgo
Outnumbered militarily and with many of its large cities occupied, Mexico could not defend itself; the country was also faced with many internal divisions, including the Caste War of Yucatán. The Treaty of Guadalupe Hidalgo, signed on February 2, 1848, by American diplomat Nicholas Trist and Mexican plenipotentiary representatives Luis G. Cuevas, Bernardo Couto, and Miguel Atristain, ended the war. The treaty gave the U.S. undisputed control of Texas, established the U.S.-Mexican border of the Rio Grande, and ceded to the United States the present-day states of California, Nevada, Utah, New Mexico, most of Arizona and Colorado, and parts of Texas, Oklahoma, Kansas, and Wyoming. In return, Mexico received $15,000,000 ($499,137,500 today) – less than half the amount the U.S. had attempted to offer Mexico for the land before the opening of hostilities – and the U.S. agreed to assume $3.25 million ($88,887,500 today) in debts that the Mexican government owed to U.S. citizens.
The acquisition was a source of controversy then, especially among U.S. politicians who had opposed the war from the start. A leading antiwar U.S. newspaper, the Whig Intelligencer, sardonically concluded that "We take nothing by conquest .... Thank God."
Jefferson Davis introduced an amendment giving the U.S. most of northeastern Mexico, which failed 44–11. It was supported by both senators from Texas (Sam Houston and Thomas Jefferson Rusk), Daniel S. Dickinson of New York, Stephen A. Douglas of Illinois, Edward A. Hannegan of Indiana, and one each from Alabama, Florida, Mississippi, Ohio, Missouri, and Tennessee. Most of the leaders of the Democratic party – Thomas Hart Benton, John C. Calhoun, Herschel V. Johnson, Lewis Cass, James Murray Mason of Virginia, and Ambrose Hundley Sevier – were opposed. An amendment by Whig Senator George Edmund Badger of North Carolina to exclude New Mexico and Upper California lost 35–15, with three Southern Whigs voting with the Democrats. Daniel Webster was bitter that four New England senators made deciding votes for acquiring the new territories.
The acquired lands west of the Rio Grande are traditionally called the Mexican Cession in the U.S., as opposed to the Texas Annexation two years earlier, though division of New Mexico down the middle at the Rio Grande never had any basis either in control or Mexican boundaries. Mexico never recognized the independence of Texas prior to the war, and did not cede its claim to territory north of the Rio Grande or Gila River until this treaty.
Prior to ratifying the treaty, the U.S. Senate made two modifications: changing the wording of Article IX (which guaranteed Mexicans living in the purchased territories the right to become U.S. citizens) and striking out Article X (which conceded the legitimacy of land grants made by the Mexican government). On May 26, 1848, when the two countries exchanged ratifications of the treaty of Guadalupe Hidalgo, they further agreed to a three-article protocol (known as the Protocol of Querétaro) to explain the amendments. The first article claimed that the original Article IX of the treaty, although replaced by Article III of the Treaty of Louisiana, would still confer the rights delineated in Article IX. The second article confirmed the legitimacy of land grants under Mexican law. The protocol was signed in the city of Querétaro by A. H. Sevier, Nathan Clifford, and Luis de la Rosa.
Article XI offered a potential benefit to Mexico, in that the US pledged to suppress the Comanche and Apache raids that had ravaged northern Mexico and pay restitutions to the victims of raids it could not prevent. However, the Indian raids did not cease for several decades after the treaty, although a cholera epidemic reduced the numbers of the Comanche in 1849. Robert Letcher, U.S. Minister to Mexico in 1850, was certain "that miserable 11th article" would lead to the financial ruin of the US if it could not be released from its obligations. The US was released from all obligations of Article XI five years later by Article II of the Gadsden Purchase of 1853.
Altered territories and citizenship
Before the secession of Texas, Mexico comprised almost 1,700,000 sq mi (4,400,000 km2), but by 1848 it was just under 800,000 square miles (2,100,000 km2). Another 30,000 square miles (78,000 km2) were sold to the U.S. in the Gadsden Purchase of 1853, so the total reduction of Mexican territory was more than 55%, or 900,000 square miles (2,300,000 km2).
Though the annexed territory was about the size of Western Europe it was sparsely populated. The land contained about 14,000 people in Alta California and about 60,000 in Nuevo México, as well as large Indian nations such as the Papago, Pima, Puebloan, Navajo, Apache, and many others. A few relocated farther south in Mexico. The great majority remained in the U.S. territory and later became U.S. citizens or their children did.
The Anglo American settlers surging into the newly conquered territories were openly contemptuous of Mexican law (a civil law system based on the law of Spain) as alien and inferior and disposed of it by enacting reception statutes at the first available opportunity. However, they recognized the value of a few aspects of Mexican law and carried them over into their new legal systems. For example, most of the southwestern states adopted community property marital property systems as well as water law.
Latinos and Indians in the annexed territories faced a loss of civil and political rights even though the Treaty of Guadalupe Hidalgo promised U.S. citizenship to all Mexican citizens living in the territory of the Mexican Cession. The U.S. government withheld citizenship from Indians in the southwest until the 1930s, despite the fact that they were citizens under Mexican law. 
Impacts of the war in the U.S.
In much of the U.S., victory and the acquisition of new land brought a surge of patriotism. Victory seemed to fulfill Democrats' belief in their country's Manifest Destiny. While Whig Ralph Waldo Emerson rejected war "as a means of achieving America's destiny," he accepted that "most of the great results of history are brought about by discreditable means." Although the Whigs had opposed the war, they made Zachary Taylor their presidential candidate in the election of 1848, praising his military performance while muting their criticism of the war.
Has the Mexican War terminated yet, and how? Are we beaten? Do you know of any nation about to besiege South Hadley [Massachusetts]? If so, do inform me of it, for I would be glad of a chance to escape, if we are to be stormed. I suppose [our teacher] Miss [Mary] Lyon would furnish us all with daggers and order us to fight for our lives...
A month before the end of the war, Polk was criticized in a United States House of Representatives amendment to a bill praising Major General Zachary Taylor for "a war unnecessarily and unconstitutionally begun by the President of the United States." This criticism, in which Congressman Abraham Lincoln played an important role with his Spot Resolutions, followed congressional scrutiny of the war's beginnings, including factual challenges to claims made by President Polk. The vote followed party lines, with all Whigs supporting the amendment. Lincoln's attack won luke-warm support from fellow Whigs in Illinois but was harshly counter-attacked by Democrats, who rallied pro-war sentiments in Illinois; Lincoln's Spot resolutions haunted his future campaigns in the heavily Democratic state of Illinois, and were cited by enemies well into his presidency.
Impacts on the American Civil War
Many of the military leaders on both sides of the American Civil War were trained at the U.S. Military Academy at West Point and had fought as junior officers in Mexico. This list includes military men fighting for the Union: Ulysses S. Grant, George B. McClellan, William T. Sherman, George Meade, William Rosecrans, and Ambrose Burnside. Military men who joined the Southern secessionists of the Confederate States of America were Robert E. Lee, Stonewall Jackson, James Longstreet, Joseph E. Johnston, Braxton Bragg, Sterling Price, and the future Confederate President Jefferson Davis. Both sides had leaders with significant experience in active combat in strategy and tactics, likely shaping ways the Civil War conflict played out.
Generally, the officers of the army were indifferent whether the annexation was consummated or not; but not so all of them. For myself, I was bitterly opposed to the measure, and to this day regard the war, which resulted, as one of the most unjust ever waged by a stronger against a weaker nation. It was an instance of a republic following the bad example of European monarchies, in not considering justice in their desire to acquire additional territory.
Grant also expressed the view that the war against Mexico had brought punishment on the United States in the form of the American Civil War:
The Southern rebellion was largely the outgrowth of the Mexican war. Nations, like individuals, are punished for their transgressions. We got our punishment in the most sanguinary and expensive war of modern times.
This view was shared by the philosopher Ralph Waldo Emerson, who towards the end of the war wrote that "The United States will conquer Mexico, but it will be as the man swallows the arsenic, which brings him down in turn. Mexico will poison us."
Despite initial objections from the Whigs and abolitionists, the war would nevertheless unite the U.S. in a common cause and was fought almost entirely by volunteers. The army swelled from just over 6,000 to more than 115,000. The majority of 12-month volunteers in Scott's army decided that a year's fighting was enough and returned to the U.S.
Veterans of the war were often broken men. "As the sick and wounded from Taylor's and Scott's campaigns made their way back from Mexico to the United States, their condition shocked the folks at home. Husbands, sons, and brothers returned in broken health, some with missing limbs."
For years afterward, U.S. veterans continued to suffer from the debilitating diseases contracted during the campaigns. The casualty rate was thus easily over 25% for the 17 months of the war; the total casualties may have reached 35–40% if later injury- and disease-related deaths are added. In this respect, the war was proportionately the most deadly in American military history. Overall, approximately 1.5% of U.S. soldiers were killed in the fighting and nearly 10% died of disease; another 12% were wounded or discharged because of disease, or both.
During the war, political quarrels in the U.S. arose regarding the disposition of conquered Mexico. A brief "All-Mexico" movement urged annexation of the entire territory. Veterans of the war who had seen Mexico at first hand were unenthusiastic. Anti-slavery elements opposed that position and fought for the exclusion of slavery from any territory absorbed by the U.S. In 1847 the House of Representatives passed the Wilmot Proviso, stipulating that none of the territory acquired should be open to slavery. The Senate avoided the issue, and a late attempt to add it to the Treaty of Guadalupe Hidalgo was defeated.
The Treaty of Guadalupe Hidalgo was the result of Nicholas Trist's unauthorized negotiations. It was approved by the U.S. Senate on March 10, 1848, and ratified by the Mexican Congress on May 25. Mexico's cession of Alta California and Nuevo México and its recognition of U.S. sovereignty over all of Texas north of the Rio Grande formalized the addition of 1.2 million square miles (3.1 million km2) of territory to the United States. In return the U.S. agreed to pay $15 million and assumed the claims of its citizens against Mexico. A final territorial adjustment between Mexico and the U.S. was made by the Gadsden Purchase in 1853. The sale of this territory was a contributing factor in the final fall of Santa Anna in Mexico for having sold Mexican patrimony.
As late as 1880, the "Republican Campaign Textbook" by the Republican Congressional Committee described the war as "Feculent, reeking Corruption" and "one of the darkest scenes in our history—a war forced upon our and the Mexican people by the high-handed usurpations of Pres't Polk in pursuit of territorial aggrandizement of the slave oligarchy."
The war was one of the most decisive events for the U.S. in the first half of the 19th century. While it marked a significant waypoint for the nation as a growing military power, it also served as a milestone especially within the U.S. narrative of Manifest Destiny. The resultant territorial gains set in motion many of the defining trends in American 19th-century history, particularly for the American West. The war did not resolve the issue of slavery in the U.S. but rather in many ways inflamed it, as potential westward expansion of the institution took an increasingly central and heated theme in national debates preceding the American Civil War. Furthermore, in doing much to extend the nation from coast to coast, the Mexican–American War was one step in the massive migrations to the West of Anglo Americans, which culminated in transcontinental railroads and the Indian wars later in the same century.
Impact of the War in Mexico
The obvious impact of the war was the loss of its northern areas and the defeat of the Mexican military. The war remains a painful historical event for Mexicans.
In Mexico City's Chapultepec Park, the Niños Héroes (Monument to the Heroic Cadets) commemorates the heroic sacrifice of six teenaged military cadets who fought to their deaths rather than surrender to American troops during the Battle of Chapultepec Castle on September 13, 1847. The monument is an important patriotic site in Mexico. On March 5, 1947, nearly one hundred years after the battle, U.S. President Harry S. Truman placed a wreath at the monument and stood for a moment of silence.
- Battles of the Mexican–American War
- Christopher Werner, maker of the "Iron Palmetto" commemorating the loss of South Carolinians in the War
- Reconquista (Mexico)
- Republic of Texas – United States relations
- Territories of Mexico
- History of Mexico
- History of New Mexico
- List of conflicts in the United States
- List of wars involving Mexico
- Mexico-United States relations
- 1846 only.
- The American Army in the Mexican War: An Overview, PBS, March 14, 2006, retrieved May 13, 2012
- The U.S.-Mexican War: Some Statistics, Descendants of Mexican War Veterans, August 7, 2004, retrieved May 13, 2012
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- Official DOD data
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- See Rives, The United States and Mexico, vol. 2, p. 658
- Pedro Santoni, "U.S.-Mexican War" in Encyclopedia of Mexico, Chicago: Fitzroy Dearborn 1997, p. 1511.
- "The Borderlands on the Eve of War". The U.S.-Mexican War. PBS.
- Brian Delay, "Independent Indians and the U.S. Mexican War" The American Historical Review, Vol 112, No. l (February 2007), p 35
- "The Annexation of Texas" U.S. Department of State. http://history.state.gov/milestones/1830-1860/Texas Annexation, Retrieved July 6, 2012
- Ida Altman, Sarah Cline, Javier Pescador, The Early History of Greater Mexico, Prentice Hall 2003, p. 333.
- Howard Lamar, editor. The Reader's Encyclopedia of the American West, (1977). Harper & Row, New York, 154.
- Lamar, The Reader's Encyclopedia of the American West, p. 154.
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- Groom, Winston "Kearny's March" Alfred A. Knopf, 2011 pp.46
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- See "Republic of Texas" at the Wayback Machine (archived April 29, 2009)
- Rives, vol. 2, pp. 165–168
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- Smith (1919) p. xi.
- Jay (1853) p. 117.
- Jay (1853) p. 119.
- Donald Fithian Stevens, Origins of Instability in Early Republican Mexico (1991) p. 11.
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- Mexican soldier Manuel Balontín, quoted in Christensen, The U.S.-Mexican War, p. 137.
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- Bronwyn Mills U.S.-Mexican war ISBN 0-8160-4932-7.
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- Justin Harvey Smith (1919). The war with Mexico vol. 1. Macmillan. p. 464.
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- Brooks (1849) p. 122.
- Brooks (1849) pp. 91, 117.
- Brooks (1849) p. 121.
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- Tucker (2013) p.718.
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- "Message of President Polk, May 11, 1846". Retrieved July 20, 2008.
Mexico has passed the boundary of the United States, has invaded our territory and shed American blood upon the American soil. She has proclaimed that hostilities have commenced, and that the two nations are now at war.
- Bauer (1992) p. 68.
- see A. Brook Caruso, The Mexican Spy Company. 1991, p. 62-79
- Jay (1853) pp. 165–166.
- Jay (1853) p. 165.
- See O'Sullivan's 1845 article "Annexation", United States Magazine and Democratic Review
- quoted in Christensen, The U.S.-Mexican War, p. 74.
- Giddings,Joshua Reed, Speeches in Congress [1841–1852], J.P. Jewett and Company, 1853, p.17
- Beveridge 1:417.
- "James K. Polk: Third Annual Message—December 7, 1847". Presidency.ucsb.edu. Retrieved May 28, 2011.
- "War News From Mexico": What the Blacks in the 1848 Painting Tell Us The Root, 2013
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- , Garrard, Lewis H., Wah-to-yah and the Taos Trail; or Prairie Travel and Scalp Dances, with a Look at Los Rancheros from Muleback and the Rocky Mountain Camp-fire, 1850, pp. 214-215; reprint, University of Oklahoma Press, Norman, 1955
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- Walker p. 98
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- Walker p. 143-144
- Walker p. 148
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- Walker p. 196
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- Walker p. 215-219
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- Brooks (1849) p. 257.
- Walker p. 233
- Walker p. 237
- Bauer (1992) pp. 190–191.
- Walker p. 238
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- Silversteen, p42
- Bauer (1992) p. 201.
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- "Urban Warfare". Battle of Monterrey.com. Retrieved May 28, 2011.
- Rip Ford's Texas Memoirs, Stephen Oates, University of Texas Press, 1963
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- Shelby Foote, The Civil War: A Narrative: Volume 1: Fort Sumter to Perryville (1958)
- Hamalainen, Pekka. The Comanche Empire. New Haven: Yale University Press. p. 232.
- Groom, Winston "Kearny's March" Alfred A. Knopf, 2011 pp.143
- Roger D. Launius (1997). Alexander William Doniphan: portrait of a Missouri moderate. University of Missouri Press. ISBN 978-0-8262-1132-3.
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- Eisenhower, John S. D. (1989). So Far from God: The U.S. War With Mexico, 1846–1848. New York: Random House. p. 295. ISBN 0-8061-3279-5.
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- "Article IX". Treaty of Guadalupe Hidalgo; February 2, 1848. Lillian Goldman Law Library.
- Hamalainen, 293-341
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- De Voto, Bernard, Year of Decision 1846 (1942), well written popular history
- Greenberg, Amy S. A Wicked War: Polk, Clay, Lincoln, and the 1846 U.S. Invasion of Mexico (2012). ISBN 9780307592699 and Corresponding Author Interview at the Pritzker Military Library on December 7, 2012
- Henderson, Timothy J. A Glorious Defeat: Mexico and Its War with the United States (2008)
- Meed, Douglas. The Mexican War, 1846–1848 (2003). A short survey.
- Merry Robert W. A Country of Vast Designs: James K. Polk, the Mexican War and the Conquest of the American Continent (2009)
- Smith, Justin Harvey. The War with Mexico, Vol 1. (2 vol 1919), full text online.
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- Bauer K. Jack. Zachary Taylor: Soldier, Planter, Statesman of the Old Southwest. Louisiana State University Press, 1985.
- Dishman, Christopher, A Perfect Gibraltar: The Battle for Monterrey, Mexico," University of Oklahoma Press, 2010 ISBN 0-8061-4140-9.
- Eisenhower, John. So Far From God: The U.S. War with Mexico, Random House (1989).
- Eubank, Damon R., Response of Kentucky to the Mexican War, 1846–1848. (Edwin Mellen Press, 2004), ISBN 978-0-7734-6495-7.
- Foos, Paul. A Short, Offhand, Killing Affair: Soldiers and Social Conflict during the Mexican-War (2002).
- Fowler, Will. Santa Anna of Mexico (2007) 527pp; a major scholarly study
- Frazier, Donald S. The U.S. and Mexico at War, Macmillan (1998).
- Hamilton, Holman, Zachary Taylor: Soldier of the Republic, (1941).
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Political and diplomatic
- Beveridge; Albert J. Abraham Lincoln, 1809–1858. Volume: 1. 1928.
- Brack, Gene M. Mexico Views Manifest Destiny, 1821–1846: An Essay on the Origins of the Mexican War (1975).
- Fowler, Will. Tornel and Santa Anna: The Writer and the Caudillo, Mexico, 1795–1853 (2000).
- Fowler, Will. Santa Anna of Mexico (2007) 527pp; the major scholarly study excerpt and text search
- Gleijeses, Piero. "A Brush with Mexico" Diplomatic History 2005 29(2): 223–254. Issn: 0145-2096 debates in Washington before war.
- Graebner, Norman A. Empire on the Pacific: A Study in American Continental Expansion. (1955).
- Graebner, Norman A. (1978). "Lessons of the Mexican War". Pacific Historical Review (University of California Press) 47 (3): 325–42. doi:10.2307/3637470. ISSN 1533-8584. JSTOR 3637470 – via JSTOR. (registration required (. ))
- Graebner, Norman A. (1980). "The Mexican War: A Study in Causation". Pacific Historical Review (University of California Press) 49 (3): 405–26. doi:10.2307/3638563. ISSN 1533-8584. JSTOR 3638563 – via JSTOR. (registration required (. ))
- Henderson, Timothy J. A Glorious Defeat: Mexico and Its War with the United States (2007), survey
- Krauze, Enrique. Mexico: Biography of Power, (1997), textbook.
- Linscott, Robert N., Editor. 1959. Selected Poems and Letters of Emily Dickinson. Anchor Books, New York. ISBN 0-385-09423-X
- Mayers, David; Fernández Bravo, Sergio A., "La Guerra Con Mexico Y Los Disidentes Estadunidenses, 1846–1848" [The War with Mexico and US Dissenters, 1846–48]. Secuencia [Mexico] 2004 (59): 32–70. Issn: 0186-0348.
- Pinheiro, John C. Manifest Ambition: James K. Polk and Civil-Military Relations during the Mexican War (2007).
- Pletcher David M. The Diplomacy of Annexation: Texas, Oregon, and the Mexican War. University of Missouri Press, 1973.
- Price, Glenn W. Origins of the War with Mexico: The Polk-Stockton Intrigue. University of Texas Press, 1967.
- Reeves, Jesse S. (1905). "The Treaty of Guadalupe-Hidalgo". The American Historical Review (American Historical Association) 10 (2): 309–24. doi:10.2307/1834723. ISSN 1937-5239. JSTOR 1834723 – via JSTOR. (registration required (. ))
- Rives, George Lockhart. The United States and Mexico, 1821–1848: a history of the relations between the two countries from the independence of Mexico to the close of the war with the United States (1913) full text online
- Rodríguez Díaz, María Del Rosario. "Mexico's Vision of Manifest Destiny During the 1847 War" Journal of Popular Culture 2001 35(2): 41–50. Issn: 0022-3840.
- Ruiz, Ramon Eduardo. Triumph and Tragedy: A History of the Mexican People, Norton 1992, textbook
- Schroeder John H. Mr. Polk's War: American Opposition and Dissent, 1846–1848. University of Wisconsin Press, 1973.
- Sellers Charles G. James K. Polk: Continentalist, 1843–1846 (1966), the standard biography vol 1 and 2 are online at ACLS e-books
- Smith, Justin Harvey. The War with Mexico. 2 vol (1919). Pulitzer Prize winner. full text online.
- Stephenson, Nathaniel Wright. Texas and the Mexican War: A Chronicle of Winning the Southwest. Yale University Press (1921).
- Weinberg Albert K. Manifest Destiny: A Study of Nationalist Expansionism in American History Johns Hopkins University Press, 1935.
- Yanez, Agustin. Santa Anna: Espectro de una sociedad (1996).
Memory and historiography
- Faulk, Odie B., and Stout, Joseph A., Jr., eds. The Mexican War: Changing Interpretations (1974)
- Rodriguez, Jaime Javier. The Literatures of the U.S.-Mexican War: Narrative, Time, and Identity (University of Texas Press; 2010) 306 pages. Covers works by Anglo, Mexican, and Mexican-American writers.
- Benjamin, Thomas. "Recent Historiography of the Origins of the Mexican War," New Mexico Historical Review, Summer 1979, Vol. 54 Issue 3, pp 169–181
- Vázquez, Josefina Zoraida. "La Historiografia Sobre la Guerra entre Mexico y los Estados Unidos," ["The historiography of the war between Mexico and the United States"] Histórica (02528894), 1999, Vol. 23 Issue 2, pp 475–485
- Calhoun, John C. The Papers of John C. Calhoun. Vol. 23: 1846, ed. by Clyde N. Wilson and Shirley Bright Cook. (1996). 598 pp
- Calhoun, John C. The Papers of John C. Calhoun. Vol. 24: December 7, 1846 – December 5, 1847 ed. by Clyde N. Wilson and Shirley Bright Cook, (1998). 727 pp.
- Conway, Christopher, ed. The U.S.-Mexican War: A Binational Reader (2010)
- Grant, Ulysses S. (1885). Personal Memoirs of U. S. Grant. New York: Charles L. Webster & Co.
- Kendall, George Wilkins (1999). Lawrence Dilbert Cress, ed. Dispatches from the Mexican War. Norman, Oklahoma: University of Oklahoma Press.
- Polk, James, K. (1910). Milo Milton Quaife, ed. The Diary of James K. Polk: During his Presidency, 1845–1849. Chicago: A. C. McClurg & Co.
- Robinson, Cecil, The View From Chapultepec: Mexican Writers on the Mexican War, University of Arizona Press (Tucson, 1989).
- Smith, Franklin (1991). Joseph E. Chance, ed. The Mexican War Journal of Captain Franklin Smith. Jackson, Mississippi: University Press of Mississippi.
- George Winston and Charles Judah, ed. (1968). Chronicles of the Gringos: The U.S. Army in the Mexican War, 1846–1848, Accounts of Eyewitnesses and Combatants. Albuquerque, New Mexico: The University of New Mexico Press.
- Webster, Daniel (1984). Charles M. Wiltse, ed. The Papers of Daniel Webster, Correspondence 6. Hanover, New Hampshire: The University Press of New England.
- "Treaty of Guadalope Hidalgo". Internet Sourcebook Project. Retrieved November 26, 2008.
- "28th Congress, 2nd session". United States House Journal. Retrieved November 26, 2008.
- "29th Congress, 1st session". United States House Journal. Retrieved November 26, 2008.
- "28th Congress, 2nd session". United States Senate Journal. Retrieved November 26, 2008.
- "29th Congress, 1st session". United States Senate Journal. Retrieved November 26, 2008.
- William Hugh Robarts, "Mexican War veterans: a complete roster of the regular and volunteer troops in the war between the United States and Mexico, from 1846 to 1848; the volunteers are arranged by states, alphabetically", BRENTANO'S (A. S. WITHERBEE & CO, Proprietors); WASHINGTON, D. C., 1887.
|Wikimedia Commons has media related to Mexican–American War.|
Guides, bibliographies and collections
- Library of Congress Guide to the Mexican War
- The Handbook of Texas Online: Mexican War
- Reading List compiled by the United States Army Center of Military History
- Mexican War Resources
- The Mexican–American War, Illinois Historical Digitization Projects at Northern Illinois University Libraries
Media and primary sources
- A Continent Divided: The U.S. - Mexico War
- Robert E. Lee Mexican War Maps in the VMI Archives
- The Mexican War and the Media, 1845–1848
- Treaty of Guadalupe Hidalgo and related resources at the U.S. Library of Congress
- Letters of Winfield Scott including official reports from the front sent to the Secretary of War
- Franklin Pierce's Journal on the March from Vera Cruz
- Mexican–American War Time line
- Animated History of the Mexican–American War
- Maps showing course of Mexican-American War at omniatlas.com
- PBS site of US-Mexican war program
- Battle of Monterrey Web Site – Complete Info on the battle
- Manifest Destiny and the U.S.-Mexican War: Then and Now
- The Mexican War
- Smithsonian teaching aids for "Establishing Borders: The Expansion of the United States, 1846–48"
- A History by the Descendants of Mexican War Veterans
- Mexican–American War
- Invisible Men: Blacks and the U.S. Army in the Mexican War by Robert E. May
- Milton Meltzer, "Bound for the Rio Grande: Traitors--Or Martyrs", Reading, video, and lesson for high school students, 1974, Zinn Education Project/Rethinking Schools.
- Google Map of The Mexican-American War of 1846-1848