Causes of World War II
|World War II|
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Among the main long-term causes of World War II were Italian fascism in the 1920s, Japanese militarism and invasions of China in the 1930s, and especially the political takeover in 1933 of Germany by Hitler and his Nazi Party and its aggressive foreign policy. The immediate cause was Britain and France declaring war on Germany after it invaded Poland in September 1939.
Problems arose in Weimar Germany that experienced strong currents of revanchism after the Treaty of Versailles that concluded its defeat in World War I in 1918. Dissatisfactions of treaty provisions included the demilitarizarion of the Rhineland, the prohibition of unification with Austria and the loss of German-speaking territories such as Danzig, Eupen-Malmedy and Upper Silesia despite Wilson's Fourteen Points, the limitations on the Reichswehr making it a token military force, the war-guilt clause, and last but not least the heavy tribute that Germany had to pay in the form of war reparations, and that become an unbearable burden after the Great Depression. The most serious internal cause in Germany was the instability of the political system, as large sectors of politically active Germans rejected the legitimacy of the Weimar Republic.
After his rise and take-over of power in 1933 to a large part based on these grievances, Adolf Hitler and the Nazis heavily promoted them and also ideas of vastly ambitious additional demands based on Nazi ideology such as uniting all Germans (and further all Germanic peoples) in Europe in a single nation; the acquisition of "living space" (Lebensraum) for primarily agrarian settlers (Blut und Boden), creating a "pull towards the East" (Drang nach Osten) where such territories were to be found and colonized, in a model that the Nazis explicitly derived from the American Manifest Destiny in the Far West and its clearing of native inhabitants; the elimination of Bolshevism; and the hegemony of an "Aryan"/"Nordic" so-called Master Race over the "sub-humans" (Untermenschen) of inferior races, chief among them Slavs and Jews.
Tensions created by those ideologies and the dissatisfactions of those powers with the interwar international order steadily increased. Italy laid claim on Ethiopia and conquered it in 1935, Japan created a puppet state in Manchuria in 1931 and expanded beyond in China from 1937, and Germany systematically flouted the Versailles treaty, reintroducing conscription in 1935 with the Stresa Front's failure after having secretly started re-armament, remilitarizing the Rhineland in 1936, annexing Austria in March 1938, and the Sudetenland in October 1938.
All those aggressive moves met only feeble and ineffectual policies of appeasement from the League of Nations and the Entente Cordiale, in retrospect symbolized by the "peace for our time" speech following the Munich Conference, that had allowed the annexation of the Sudeten from interwar Czechoslovakia. When the German Führer broke the promise he had made at that conference to respect that country's future territorial integrity in March 1939 by sending troops into Prague, its capital, breaking off Slovakia as a German client state, and absorbing the rest of it as the "Protectorate of Bohemia-Moravia", Britain and France tried to switch to a policy of deterrence.
As Nazi attentions turned towards resolving the "Polish Corridor Question" during the summer of 1939, Britain and France committed themselves to an alliance with Poland, threatening Germany with a two-front war. On their side, the Germans assured themselves of the support of the USSR by signing a non-aggression pact with them in August, secretly dividing Eastern Europe into Nazi and Soviet spheres of influence.
The stage was then set for the Danzig crisis to become the immediate trigger of the war in Europe started on 1 September 1939. Following the Fall of France in June 1940, the Vichy regime signed an armistice, which tempted the Empire of Japan to join the Axis powers and invade French Indochina to improve their military situation in their war with China. This provoked the then neutral United States to respond with an embargo. The Japanese leadership, whose goal was Japanese domination of the Asia-Pacific, thought they had no option but to pre-emptively strike at the US Pacific fleet, which they did by attacking Pearl Harbor on 7 December 1941.
- 1 Ideologies, doctrines, and philosophies
- 2 Interrelations and economics
- 3 Specific developments
- 3.1 Nazi dictatorship
- 3.2 Re-militarization of the Rhineland
- 3.3 Italian invasion of Ethiopia
- 3.4 Spanish Civil War
- 3.5 Second Sino-Japanese War
- 3.6 Anschluss
- 3.7 Munich Agreement
- 3.8 Italian invasion of Albania
- 3.9 Soviet–Japanese Border War
- 3.10 Danzig crisis
- 3.11 Invasion of the Soviet Union
- 3.12 Attack on Pearl Harbor
- 4 See also
- 5 References
- 6 Further reading
- 7 External links
Ideologies, doctrines, and philosophies
The internationalist-minded, radical Bolsheviks seized power in Russia in November 1917, with the goal of overthrowing capitalism across the world. They supported Communist parties in many lands and helped set up similar regimes in Hungary and Bavaria, Azerbaijan, Armenia and Georgia. This caused many Europeans to fear that a violent Communist revolution would overwhelm their own countries. The Red expansion was stopped outside Warsaw by the Polish army, and by 1920 there was a corridor of border states just west of Russia that rejected Communism. However they feuded among themselves and such alliances they formed like the Little Entente were unstable.
Both Italian and German fascism were in part a reaction to international communist and socialist uprisings, in conjunction with nationalist fears of a Slavic empire. A further factor in Germany was the success of Freikorps (voluntary paramilitary groups of World War I veterans) in crushing the Bolshevik Bavarian Soviet Republic in Munich in 1919. Many of these veterans became early components of the Nazis' SA ("Stormtroopers"), which would be the party's troops in the street warfare with the Communist armed militia in the decade before 1933. The street violence would help shift moderate opinion towards the need for Germany to find an anti-Communist strongman to restore stability to German life.
Expansionism is the doctrine of expanding the territorial base (or economic influence) of a country, usually by means of military aggression. In Europe, Italy under Benito Mussolini sought to create a New Roman Empire based around the Mediterranean. It invaded Albania in early 1939, at the start of the war, and later invaded Greece. Italy had also invaded Ethiopia as early as 1935. This provoked angry words and an oil embargo from the League of Nations, which failed.
Under the Nazi regime, Germany began its own program of expansion, seeking to restore the "rightful" boundaries of historic Germany. As a prelude toward these goals the Rhineland was remilitarized in March 1936.
Also, of importance was the idea of a Greater Germany, supporters hoped to unite the German people under one nation state, which included all territories where Germans lived, regardless of whether they happened to be a minority in a particular territory. After the Treaty of Versailles, a unification between Germany and a newly formed German-Austria, a successor rump state of Austria-Hungary, was prohibited by the Allies despite the majority of Austrian Germans supporting such a union.
A highly militaristic and aggressive national ideology prevailed in Germany, Japan and Italy.
Twentieth-century events marked the culmination of a millennium-long process of intermingling between Germans and Slavs. Over the centuries, many Germans had settled in the east (examples being the Volga Germans invited to Russia by Catherine the Great, and the Ostsiedlung in medieval times). Such migratory patterns created enclaves and blurred ethnic frontiers. The rise of nationalism in the 19th made race a centerpiece of political loyalty. The rise of the nation-state had given way to the politics of identity, including Pan-Germanism and Pan-Slavism. Furthermore, Social-Darwinist theories framed the coexistence as a "Teuton vs. Slav" struggle for domination, land and limited resources. Integrating these ideas into their own world-view, the Nazis believed that the Germans, the "Aryan race", were the master race and that the Slavs were inferior.
Interrelations and economics
Problems with the Treaty of Versailles
The Treaty of Versailles was neither lenient enough to appease Germany, nor harsh enough to prevent it from becoming the dominant continental power again. The treaty placed the blame, or "war guilt" on Germany and Austria-Hungary, and punished them for their "responsibility" rather than working out an agreement that would assure long-term peace. The treaty provided for harsh monetary reparations, separated millions of ethnic Germans into neighboring countries, territorial dismemberment, and caused mass ethnic resettlement. In an effort to pay war reparations to Britain and France, the Weimar Republic printed trillions of marks, causing extremely high inflation of the German currency (see Hyperinflation in the Weimar Republic).
The treaty created bitter resentment towards the victors of World War I, who had promised the people of Germany that U.S. President Woodrow Wilson's Fourteen Points would be a guideline for peace; however, the US played a minor role in World War I and Wilson could not convince the Allies to agree to adopt his Fourteen Points. Many Germans felt that the German government had agreed to an armistice based on this understanding, while others felt that the German Revolution of 1918–1919 had been orchestrated by the "November criminals" who later assumed office in the new Weimar Republic.
The German colonies were taken during the war, and Italy took the southern half of Tyrol after an armistice had been agreed upon. The war in the east ended with the defeat and collapse of Russian Empire, and German troops occupied large parts of Eastern and Central Europe (with varying degree of control), establishing various client states such as a kingdom of Poland and the United Baltic Duchy. After the destructive and indecisive battle of Jutland (1916) and the mutiny of its sailors in 1917, the Kaiserliche Marine spent most of the war in port, only to be turned over to the allies and scuttled at surrender by its own officers. The lack of an obvious military defeat was one of the pillars that held together the Dolchstosslegende ("Stab-in-the-back myth") and gave the Nazis another propaganda tool at their disposal.
French security demands
French security demands, such as reparations, coal payments, and a demilitarized Rhineland, took precedent at the Paris Peace Conference in 1919 and shaped the Treaty of Versailles by severely punishing Germany; however, Austria found the treaty to be unjust which encouraged Hitler's popularity. Ginsberg argues, "France was greatly weakened and, in its weakness and fear of a resurgent Germany, sought to isolate and punish Germany....French revenge would come back to haunt France during the Nazi invasion and occupation twenty years later."
Paris Peace Conference (1919)
As World War I ended in 1918, France, along with the other victor countries, were in a desperate situation regarding their economies, security, and morale. The Paris Peace Conference of 1919 was their chance to punish Germany for starting the war. The war "must be someone's fault – and that's a very natural human reaction" analyzed historian Margaret MacMillan. Germany was charged with the sole responsibility of starting World War I. The War Guilt Clause was the first step towards a satisfying revenge for the victor countries, namely France, against Germany. France understood that its position in 1918 was "artificial and transitory". Thus, Clemenceau, the French leader at the time, worked to gain French security via the Treaty of Versailles.
The two main provisions of the French security agenda were reparations from Germany in the form of money and coal and a detached German Rhineland. The French government printed excess currency, which created inflation, to compensate for the lack of funds in addition to borrowing money from the United States. Reparations from Germany were necessary to stabilize the French economy. France also demanded that Germany give France their coal supply from the Ruhr to compensate for the destruction of French coalmines during the war. Because France feared for its safety as a country, the French demanded an amount of coal that was a "technical impossibility" for the Germans to pay back. France wanted the German Rhineland demilitarized because that would hinder a German attack. This gave France a physical security barrier between itself and Germany. The inordinate amount of reparations, coal payments, and the principle of a demilitarized Rhineland were viewed by the Germans to be insulting and unreasonable.
Germany's reaction to Treaty of Versailles
"No postwar German government believed it could accept such a burden on future generations and survive ...". Paying reparations is a classic punishment of war but in this instance it was the "extreme immoderation" (History) that caused German resentment. Germany made its last World War I reparation payment on 3 October 2010, ninety-two years after the end of World War I. Germany also fell behind in their coal payments. They fell behind because of a passive resistance movement against the French. In response, the French invaded the Ruhr, the region filled with German coal, and occupied it. At this point the majority of Germans were enraged with the French and placed the blame for their humiliation on the Weimar Republic. Adolf Hitler, a leader of the Nazi Party, attempted a coup d'état against the republic to establish a Greater German Reich known as the Beer Hall Putsch in 1923. Although this failed, Hitler gained recognition as a national hero amongst the German population. The demilitarized Rhineland and additional cutbacks on military infuriated the Germans. Although it is logical that France would want the Rhineland to be a neutral zone, the fact that France had the power to make that desire happen merely added onto the resentment of the Germans against the French. In addition, the Treaty of Versailles dissolved the German general staff and possession of navy ships, aircraft, poison gas, tanks, and heavy artillery was made illegal. The humiliation of being bossed around by the victor countries, especially France, and being stripped of their prized military made the Germans resent the Weimar Republic and idolize anyone who stood up to it.
Competition for resources and markets
Other than a few coal and iron deposits, and a small oil field on Sakhalin Island, Japan lacked strategic mineral resources. At the start of the 20th century in the Russo-Japanese War, Japan had succeeded in pushing back the East Asian expansion of the Russian Empire in competition for Korea and Manchuria.
Japan's goal after 1931 was economic dominance of most of East Asia, often expressed in Pan-Asian terms of "Asia for the Asians.". Japan was determined to dominate the China market, which the U.S. and other European powers had been dominating. On October 19, 1939, the American Ambassador to Japan, Joseph C. Grew, in a formal address to the America-Japan Society stated:
- the new order in East Asia has appeared to include, among other things, depriving Americans of their long established rights in China, and to this the American people are opposed ... American rights and interests in China are being impaired or destroyed by the policies and actions of the Japanese authorities in China."
In 1937 Japan invaded Manchuria and China proper. Under the guise of the Greater East Asia Co-Prosperity Sphere, with slogans as "Asia for the Asians!" Japan sought to remove the Western powers' influence in China and replace it with Japanese domination.
The ongoing conflict in China led to a deepening conflict with the U.S., where public opinion was alarmed by events such as the Nanking Massacre and growing Japanese power. Lengthy talks were held between the U.S. and Japan. When Japan moved into the southern part of French Indochina, President Roosevelt chose to freeze all Japanese assets in the U.S. The intended consequence of this was the halt of oil shipments from the U.S. to Japan, which had supplied 80 percent of Japanese oil imports. The Netherlands and Britain followed suit. With oil reserves that would last only a year and a half during peace time (much less during wartime), this ABCD line left Japan two choices: comply with the U.S.-led demand to pull out of China, or seize the oilfields in the East Indies from the Netherlands. The Japan government deemed it unacceptable to retreat from China.
Problems with the League of Nations
The League of Nations was an international organization founded after World War I to prevent future wars. The League's methods included disarmament; preventing war through collective security; settling disputes between countries through negotiation diplomacy; and improving global welfare. The diplomatic philosophy behind the League represented a fundamental shift in thought from the preceding century. The old philosophy of "concert of nations", growing out of the Congress of Vienna (1815), saw Europe as a shifting map of alliances among nation-states, creating a balance of power maintained by strong armies and secret agreements. Under the new philosophy, the League was a government of governments, with the role of settling disputes between individual nations in an open and legalist forum. The impetus for the founding of the League came from U.S. President Wilson, though the United States never joined. This lessened the power and credibility of the League—the addition of a burgeoning industrial and military world power would have added more force behind the League's demands and requests.
The League lacked an armed force of its own and so depended on the members to enforce its resolutions, uphold economic sanctions that the League ordered, or provide an army when needed for the League to use. However, they were often very reluctant to do so.
After numerous notable successes and some early failures in the 1920s, the League ultimately proved incapable of preventing aggression by the Axis powers in the 1930s. The reliance upon unanimous decisions, the lack of an armed force, the absence of the U.S., and the continued self-interest of its leading members meant that this failure was arguably inevitable.
The Mason-Overy Debate: "The Flight into War" theory
In the late 1980s the British historian Richard Overy was involved in a historical dispute with Timothy Mason that mostly played out over the pages of the Past and Present journal over the reasons for the outbreak of World War II in 1939. Mason had contended that a "flight into war" had been imposed on Adolf Hitler by a structural economic crisis, which confronted Hitler with the choice of making difficult economic decisions or aggression. Overy argued against Mason's thesis, maintaining that though Germany was faced with economic problems in 1939, the extent of these problems cannot explain aggression against Poland and the reasons for the outbreak of war were due to the choices made by the Nazi leadership.
Mason had argued that the German working-class was always opposed to the Nazi dictatorship; that in the over-heated German economy of the late 1930s, German workers could force employers to grant higher wages by leaving for another firm that would grant the desired wage increases; that this was a form of political resistance and this resistance forced Adolf Hitler to go to war in 1939. Thus, the outbreak of the Second World War was caused by structural economic problems, a "flight into war" imposed by a domestic crisis. The key aspects of the crisis were according to Mason, a shaky economic recovery was threatened by a rearmament program that was overwhelming the economy and in which the Nazi regime's nationalist bluster limited its options. In this way, Mason articulated a Primat der Innenpolitik ("primacy of domestic politics") view of World War II's origins through the concept of social imperialism. Mason's Primat der Innenpolitik thesis was in marked contrast to the Primat der Außenpolitik ("primacy of foreign politics) usually used to explain World War II. In Mason's opinion, German foreign policy was driven by domestic political considerations, and the launch of World War II in 1939 was best understood as a "barbaric variant of social imperialism".
Mason argued that "Nazi Germany was always bent at some time upon a major war of expansion." However, Mason argued that the timing of a such a war was determined by domestic political pressures, especially as relating to a failing economy, and had nothing to do with what Hitler wanted. In Mason's view in the period between 1936–41, it was the state of the German economy, and not Hitler's 'will' or 'intentions' that was the most important determinate on German decision-making on foreign policy. Mason argued that the Nazi leaders were deeply haunted by the November Revolution of 1918, and was most unwilling to see any fall in working class living standards out of the fear that it might provoke another November Revolution. According to Mason, by 1939, the "overheating" of the German economy caused by rearmament, the failure of various rearmament plans produced by the shortages of skilled workers, industrial unrest caused by the breakdown of German social policies, and the sharp drop in living standards for the German working class forced Hitler into going to war at a time and place not of his choosing. Mason contended that when faced with the deep socio-economic crisis the Nazi leadership had decided to embark upon a ruthless 'smash and grab' foreign policy of seizing territory in Eastern Europe which could be pitilessly plundered to support living standards in Germany. Mason described German foreign policy as driven by an opportunistic 'next victim' syndrome after the Anschluss, in which the "promiscuity of aggressive intentions" was nurtured by every successful foreign policy move. In Mason's opinion, the decision to sign the German-Soviet Non-Aggression Pact with the Soviet Union and to attack Poland and the running of the risk of a war with Britain and France were the abandonment by Hitler of his foreign policy program outlined in Mein Kampf forced on him by his need to stop a collapsing German economy by seizing territory abroad to be plundered.
For Overy, the problem with Mason's thesis was that it rested on the assumption that in a way not shown by records, information was passed on to Hitler about the Reich's economic problems. Overy argued that there was a difference between economic pressures induced by the problems of the Four Year Plan and economic motives to seize raw materials, industry and foreign reserves of neighboring states as a way of accelerating the Four Year Plan. Overy asserted that the repressive capacity of the German state as a way of dealing with domestic unhappiness was somewhat downplayed by Mason. Finally, Overy argued that there is considerable evidence that the German state felt they could master the economic problems of rearmament; as one civil servant put it in January 1940 "we have already mastered so many difficulties in the past, that here too, if one or other raw material became extremely scarce, ways and means will always yet be found to get out of a fix".
Hitler and his Nazis took full control of Germany in 1933–34 (Machtergreifung), turning it into a dictatorship with a highly hostile outlook toward the Treaty of Versailles and Jews. It solved its unemployment crisis by heavy military spending.
Hitler's diplomatic strategy was to make seemingly reasonable demands, threatening war if they were not met. When opponents tried to appease him, he accepted the gains that were offered, then went to the next target. That aggressive strategy worked as Germany pulled out of the League of Nations (1933), rejected the Versailles Treaty and began to re-arm (1935) with the Anglo-German Naval Agreement, won back the Saar (1935), re-militarized the Rhineland (1936), formed an alliance ("axis") with Mussolini's Italy (1936), sent massive military aid to Franco in the Spanish Civil War (1936–39), seized Austria (1938), took over Czechoslovakia after the British and French appeasement of the Munich Agreement of 1938, formed a peace pact with Stalin's Russia in August 1939, and finally invaded Poland in September 1939.
Re-militarization of the Rhineland
In violation of the Treaty of Versailles and the spirit of the Locarno Pact and the Stresa Front, Germany re-militarized the Rhineland on March 7, 1936. It moved German troops into the part of western Germany where, according to the Versailles Treaty, they were not allowed. France could not act because of political instability at the time. According to his official Biography, King Edward VIII, who thought the Versailles provision was unjust,ordered the government to stand down. 
Italian invasion of Ethiopia
After the Stresa Conference and even as a reaction to the Anglo-German Naval Agreement, Italian dictator Benito Mussolini attempted to expand the Italian Empire in Africa by invading the Ethiopian Empire (also known as Abyssinia). The League of Nations declared Italy the aggressor and imposed sanctions on oil sales that proved ineffective. Italy annexed Ethiopia in May 7 and merged Ethiopia, Eritrea, and Somaliland into a single colony known as Italian East Africa. On June 30, 1936, Emperor Haile Selassie gave a stirring speech before the League of Nations denouncing Italy's actions and criticizing the world community for standing by. He warned that "It is us today. It will be you tomorrow". As a result of the League's condemnation of Italy, Mussolini declared the country's withdrawal from the organization.
Spanish Civil War
As to other works of art, Pablo Picasso painted Guernica Germany and Italy lent support to the Nationalists led by general Francisco Franco in Spain while the Soviet Union supported the existing government, the Spanish Republic. Both sides experimented with new weapons and tactics. The League of Nations was never involved, and the major powers remained neutral and tried (with little success) to stop arms shipments into Spain. The Nationalists won in 1939. Spain negotiated on joining the Axis but remained neutral during World War II, and did business with both sides. It also sent a volunteer unit to help the Germans against the USSR. In the 1940s and 1950s it was seen as a prelude to World War II. It prefigured the war as it changed into an antifascists contest after 1941, but it bore no resemblance and to the war that started in 1939 and had no major role in causing the war.
Second Sino-Japanese War
In 1931 Japan took advantage of China's weakness in the Warlord Era and fabricated the Mukden Incident in 1931 to set up the puppet state of Manchukuo in Manchuria, with Puyi, who had been the last emperor of China, as its emperor. In 1937 the Marco Polo Bridge Incident triggered the Second Sino-Japanese War.
The invasion was launched by the bombing of many cities such as Shanghai, Nanjing and Guangzhou. The latest, which began on 22 and 23 September 1937, called forth widespread protests culminating in a resolution by the Far Eastern Advisory Committee of the League of Nations. The Imperial Japanese Army captured the Chinese capital city of Nanjing, and committed war crimes in the Nanjing massacre. The war tied down large numbers of Chinese soldiers, so Japan set up three different Chinese puppet states to enlist some Chinese support.
The Anschluss was the 1938 annexation by threat of force of Austria into Germany. Historically, the Pan-Germanism idea of creating a Greater Germany to include all ethnic Germans into one nation-state was popular for Germans in both Austria and Germany.
One of the Nazi party's points was "We demand the unification of all Germans in the Greater Germany on the basis of the people's right to self-determination."
The Stresa Front of 1935 between Britain, France and Italy had guaranteed the independence of Austria, but after the creation of the Rome-Berlin Axis Mussolini was much less interested in upholding its independence.
The Austrian government resisted as long as possible, but had no outside support and finally gave in to Hitler's fiery demands. No fighting occurred as most Austrians were enthusiastic, and Austria was fully absorbed as part of Germany. Outside powers did nothing. Italy had little reason for continued opposition to Germany, and was if anything drawn in closer to the Nazis.
The Sudetenland was a predominantly German region inside Czechoslovakia alongside its border with Germany. Its more than 3 million ethnic Germans comprised almost a quarter of the population of Czechoslovakia. In the Treaty of Versailles it was given to the new Czechoslovak state against the wishes of much of the local population. The decision to disregard their right to self determination was based on French intent to weaken Germany. Much of Sudetenland was industrialized.
Czechoslovakia had a modern army of 38 divisions, backed by a well-noted armament industry (Škoda) as well as military alliances with France and Soviet Union. However its defensive strategy against Germany was based on the mountains of the Sudetenland.
Hitler pressed for the Sudetenland's incorporation into the Reich, supporting German separatist groups within the Sudeten region. Alleged Czech brutality and persecution under Prague helped to stir up nationalist tendencies, as did the Nazi press. After the Anschluss, all German parties (except German Social-Democratic party) merged with the Sudeten German Party (SdP). Paramilitary activity and extremist violence peaked during this period and the Czechoslovakian government declared martial law in parts of the Sudetenland to maintain order. This only complicated the situation, especially now that Slovakian nationalism was rising, out of suspicion towards Prague and Nazi encouragement. Citing the need to protect the Germans in Czechoslovakia, Germany requested the immediate annexation of the Sudetenland.
In the Munich Agreement of September 30, 1938, British, French and Italian prime ministers appeased Hitler by giving him what he wanted, hoping he would not want any more. The conferring powers allowed Germany to move troops into the region and incorporate it into the Reich "for the sake of peace." In exchange for this, Hitler gave his word that Germany would make no further territorial claims in Europe. Czechoslovakia was not allowed to participate in the conference. When the French and British negotiators informed the Czechoslovak representatives about the agreement, and that if Czechoslovakia would not accept it, France and Britain would consider Czechoslovakia to be responsible for war, President Edvard Beneš capitulated. Germany took the Sudetenland unopposed.
German occupation and Slovak independence
In March 1939, breaking the Munich Agreement, German troops invaded Prague, and with the Slovaks declaring independence, the country of Czechoslovakia disappeared. The entire ordeal was the last show of the French and British policy of appeasement.
Italian invasion of Albania
After the German occupation of Czechoslovakia, Benito Mussolini feared for Italy becoming a second-rate member of the Axis. Rome delivered Tirana an ultimatum on March 25, 1939, demanding that it accede to Italy's occupation of Albania. King Zog refused to accept money in exchange for countenancing a full Italian takeover and colonization of Albania. On April 7, 1939, Italian troops invaded Albania. Albania was occupied after a 3 days campaign with minimal resistance offered by the Albanian forces.
Soviet–Japanese Border War
In 1939, the Japanese attacked west from Manchuria into the Mongolian People's Republic, following the earlier Battle of Lake Khasan in 1938. They were decisively beaten by Soviet units under General Georgy Zhukov. Following this battle, the Soviet Union and Japan were at peace until 1945. Japan looked south to expand its empire, leading to conflict with the United States over the Philippines and control of shipping lanes to the Dutch East Indies. The Soviet Union focused on her western border, but leaving 1 million to 1.5 million troops to guard the frontier with Japan.
After the final fate of Czechoslovakia proved that the Führer's word could not be trusted, Britain and France decided to change tack. They decided any further unilateral German expansion would be met by force. The natural next target for the Third Reich's further expansion was Poland, whose access to the Baltic sea had been carved out of West Prussia by the Versailles treaty, making East Prussia an exclave. The main port of the area, Danzig, had been made a free city-state under Polish influence guaranteed by the League of Nations, a stark reminder to German nationalists of the Napoleonic free city established after the French emperor's crushing victory over Prussia in 1807.
After taking power, the Nazi government made efforts to establish friendly relations with Poland, resulting in the signing of the ten-year German–Polish Non-Aggression Pact with the Piłsudski regime in 1934. In 1938, Poland participated in the dismemberment of Czechoslovakia by annexing Zaolzie. In 1939, Hitler claimed extra-territoriality for the Reichsautobahn Berlin-Königsberg and a change in Danzig's status, in exchange for promises of territory in Poland's neighbours and a 25-year extension of the non-aggression pact. Poland refused, fearing losing de facto access to the sea, subjugation as a German satellite state or client state, and future further German demands.  In August 1939, Hitler delivered an ultimatum to Poland on Danzig's status.
Polish alliance with the Entente
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In March 1939, Britain and France guaranteed the independence of Poland. Hitler's claims in the summer of 1939 on Danzig and the Polish provoked yet another international crisis. On August 25, Britain signed the Polish-British Common Defence Pact.
Nominally, the Molotov-Ribbentrop Pact was a non-aggression treaty between Germany and the Soviet Union. It was signed in Moscow on August 23, 1939, by the Soviet foreign minister Vyacheslav Molotov and the German foreign minister Joachim von Ribbentrop.
In 1939, neither Germany nor the Soviet Union were ready to go to war with each other. The Soviet Union had lost territory to Poland in 1920. Although officially labeled a "non-aggression treaty", the pact included a secret protocol, in which the independent countries of Finland, Estonia, Latvia, Lithuania, Poland and Romania were divided into spheres of interest of the parties. The secret protocol explicitly assumed "territorial and political rearrangements" in the areas of these countries.
Subsequently all the mentioned countries were invaded, occupied, or forced to cede part of their territory by either the Soviet Union, Germany, or both.
Invasion of Poland
Between 1919 and 1939 Poland pursued a policy of balance between Soviet Union and Nazi Germany seeking non-aggression treaties with both In early 1939 Germany demanded that Poland join the Anti-Comintern Pact as a satellite state of Germany. Poland, fearing a loss of independence, refused, and Hitler told his generals on 23 May 1939 that the reason for invading Poland was "Danzig is not the object to which it goes. It is for us the extension of the living space in the East." To deter Hitler, Britain and France announced that an invasion meant war, and tried to convince the Soviet Union to join in this deterrence. Moscow played along but found it could gain control of the Baltic states and parts of Poland by allying with Germany, which it did in August 1939. London's deterrence had failed, but Hitler did not expect a wider war. Germany invaded Poland on September 1, 1939 and rejected the British and French demands that it withdraw resulting in their declaration of war on September 3, 1939 in accordance to the defense treaties they signed with Poland and publicly announced.
Invasion of the Soviet Union
Germany attacked the Soviet Union in June 1941. Hitler believed that the Soviet Union could be defeated in a fast-paced and relentless assault that capitalized on the Soviet Union's ill-prepared state, and hoped that success there would bring Britain to the negotiation table, ending the war altogether. Hitler further wanted to preempt an attack by the Soviet Union, and in doing so catch the Soviets off-guard.
Attack on Pearl Harbor
Traditionally, the US government and the American public in general had been supportive of China, condemning the colonialist policies of the European powers and Japan in that country, and promoting a so-called Open Door Policy. Also, many Americans viewed the Japanese as an aggressive or inferior race, or both. The Nationalist Government of Chiang Kai-Shek held close relations with the United States, which opposed Japan's invasion of China in 1937 that it considered an illegal violation of the sovereignty of the Republic of China, and offered the Nationalist Government diplomatic, economic, and military assistance during its war against Japan. Diplomatic friction between the US and Japan manifested itself in events like the Panay incident in 1937 and the Allison incident in 1938.
Reacting to Japanese pressure on French authorities of French Indochina to stop trade with China, the U.S. began restricting trade with Japan in July 1940. The cutoff of all oil shipments in 1941 was decisive, for the U.S., Britain and the Netherlands provided almost all of Japan's oil. In September 1940, the Japanese invaded Vichy French Indochina and occupied Tonkin in order to prevent China from importing arms and fuel through French Indochina along the Sino-Vietnamese Railway, from the port of Haiphong through Hanoi to Kunming in Yunnan. This tightening of the blockade of China made a continuation of the drawn-out Battle of South Guangxi unnecessary. The agreement also allowed Japan to station troops in the rest of Indochina, though this did not happen immediately.
Taking advantage of the situation, Thailand launched the Franco-Thai War in October 1940. In November 1940, American military aviator Claire Lee Chennault upon observing the dire situation in the air war between China and Japan, set out to organize a volunteer squadron of American fighter pilots to fight alongside the Chinese against Japan, known as the Flying Tigers. US President Franklin D. Roosevelt accepted dispatching them to China in early 1941. However, they only became operational shortly after the attack on Pearl Harbor.
Japan stepped in as a mediator for the French-Thai war in May 1941, allowing its ally to occupy bordering provinces in Cambodia and Laos. In July 1941, as operation Barbarossa had neutralised the Soviet threat, the faction of the Japanese military junta supporting the "Southern Strategy", pushed through the occupation of the rest of French Indochina.
The United States reacted by seeking to bring the Japanese war effort to a complete halt by imposing a full embargo on all trade between the United States to Japan on 1 August 1941, demanding that Japan withdraw all troops from both China and Indochina. Japan was dependent on the United States for 80 percent of its oil, resulting in an economic and military crisis for Japan that could not continue its war effort with China without access to petroleum and oil products.
On 7 December 1941, without any prior declaration of war, the Imperial Japanese Navy attacked Pearl Harbor with the aim of destroying the main American battle fleet at anchor. At the same time, other Japanese forces attacked the U.S.-held Philippines and the British Empire in Malaya, Singapore, and Hong Kong. These attacks led both the USA and the United Kingdom to declare war upon Japan the next day.
Four days later the U.S was brought into the European war when on December 11, 1941, Nazi Germany and Fascist Italy declared war on the United States. Hitler chose to declare that the Tripartite Pact required that Germany follow Japan's declaration of war; although American destroyers escorting convoys and German U-boats were already de facto at war in the Battle of the Atlantic. This declaration effectively ended isolationist sentiment in the U.S. and the United States immediately reciprocated, formally entering the war in Europe.
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