Tanks in World War II
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Tanks were an important weapons system in World War II. Although tanks were the subject of widespread research in the inter-war years, production was limited to relatively small numbers in a few countries. However, during WWII most armies employed tanks, and production levels reached thousands each month. Tank usage, doctrine and production varied widely among the combatant nations. By war's end, some consensus was emerging regarding tank doctrine and design.
The tank was invented by the British in World War I, with nearly simultaneous development in France. Tanks of the first World War reflected the novelty of the idea and the primitive state of the automotive industry. WW1 tanks moved at a walking pace, were relatively unreliable, and were employed according to doctrines still being worked out at war's end.
The doctrine of armored warfare changed radically in the inter-war years as Armies sought ways to avoid the deadlock imposed by modern firepower and looked for the means to restore offensive power on the battlefield. Initially, tanks had been used for close support of infantry, but as modern mechanized doctrine was developed by several Armies, tanks became an essential part of the combined-arms team. In addition to infantry support, tanks fulfilled traditional cavalry roles, provided mobile artillery support, and adopted combat engineering roles.
Tank design tank gradually improved in the inter-war period also. Reflecting the growth of the automotive industry, tanks improved their engines, transmissions, and track systems. By the beginning of the war, tanks were available that could travel hundreds of miles on their tracks with a limited number of breakdowns.
During the war, much more rapid changes in design took place. In particular, the gun-vs-armor race of the war led to rapid increases in firepower and armor thickness and design.
Major Themes 
The United Kingdom, the United States, the USSR, France and Italy produced significant numbers of tanks before and during World War II. The early tanks of Germany were inferior to many of their opponent's tanks in the areas of armour and firepower. However, it was in their tactical employment that German tanks dominated all rivals early in the war. German doctrine stressed the use of rapid movement, mission-type orders and combined-arms tactics involving mobile infantry and air support; this doctrine was popularly called Blitzkrieg. This doctrine required the Germans to equip their tanks with radios, which provided unmatched command and control for flexible employment.
In contrast, for example, almost 80 percent of French tanks lacked radios, essentially because their battle doctrine was based on a more slow-paced, deliberate conformance to planned movements. This required fewer radios at all levels. French tanks generally outclassed German tanks in firepower and armour in the 1940 campaign, but their poor command and control doctrine negated these advantages. By 1943, two-way radio was nearly universal.
A trend towards heavier tanks was unmistakable as the war proceeded. In 1939, most tanks had maximum armour of 30 mm or less, with guns no heavier than 37–47 mm. Medium tanks of 1939 weighed around 20 tonnes. By 1945, typical medium tanks had maximum armour over 60 mm thick, with guns in the 75–85 mm range and weights of 30 to 45 tonnes. Light tanks, which dominated most armies early in the war, gradually faded out of front line service.
Turrets, which had always been considered, but were not previously a universal feature on tanks, were recognised as essential. It was appreciated that if the tank's gun was to be used to engage both 'soft' (unarmored) and armoured targets, then it needed to be as large and powerful as possible, making one large gun with an all-round field of fire vital. Also, mounting the gun in a turret ensured that the tank could fire from behind some cover. Hull-mounted guns required that most of the vehicle be exposed to enemy fire. Multiple-turreted or multi-gun designs such as the Soviet T-35, American Medium Tank M3, French Char B or British A9 Cruiser Mk I slowly became less common during World War II. It was recognized that a tank crew could not effectively control the fire of several weapons; also, newer dual-purpose guns eliminated the need for multiple weapons. Most tanks still retained a hull machine gun, and usually one or more machineguns in the turret, to protect them from infantry at short range.
Tanks were adapted to a wide range of military jobs, including engineering tasks. Specialized models, such as flame-thrower tanks, recovery tanks for towing disabled tanks, and command tanks with extra radios were also used. Some of these tank variants live on as other classes of armoured fighting vehicle, no longer called "tanks". All major combatant powers also developed tank destroyers and assault guns - armoured vehicles carrying large calibre guns, but often no turrets. Turreted vehicles are expensive to manufacture compared to nonturreted vehicles. One trend seen in World War II was the usage of older, lighter tank chassis to mount larger weapons in fixed casemates as tank destroyers or assault guns. For example, the Soviet T-34 could mount an 85 mm gun in the turret, but the same chassis could carry the much more effective 100 mm gun in a fixed casemate as the SU-100. Likewise, the obsolete German Panzer II light tank, too vulnerable for a direct fire role, was modified to take a powerful 75 mm PAK-40 gun in an open-topped, fixed casemate as the Marder II self-propelled artillery piece.
Tanks of the Major Combatants 
Soviet Union 
The Soviet Union began and ended the war with more tanks than the rest of the world combined (18,000-22,000). At the start of World War II the most common tank in Soviet service was the Vickers-based T-26, armed with a 45mm cannon capable of penetrating most German tanks at normal combat ranges. Few had radios. The design was mechanically sound although incapable of further development. The BT tank series, based on the Christie suspension system, were usually armed with the same 45 mm gun and were the most mobile tanks in the world. Close-support versions of both tanks existed, armed with 76.2 mm howitzers. However, the BT was at the end of its design life. The Red Army also fielded thousands of light recon tanks such as the amphibious T-37 and T-38. These had limited combat value; although highly mobile, they were armed only with 7.62 mm machine guns and had very thin armour. The Red Army also had about 400 T-28 medium tanks, which were in most respects equal to the German Pzkw-IV. Again, though, this design dated from 1931 and was obsolescent.
The Soviet Union ended the 1930s with a huge fleet of tanks almost completely derived from foreign designs, but before 1941 developed some of the most important trend-setting tanks of the war. The problem the Soviet tank force faced in 1941 was not primarily the technical quality of its vehicles, but the very poor state of maintenance, the appalling lack of readiness, and the poor command situation brought on by the purges. The Red Army had in 1940 adopted an advanced doctrine that it was simply incapable of executing.
Several excellent designs were just entering production in 1940-41. On the eve of war, the Red Army had embarked on two closely related projects to reorganize its mechanized forces and re-equip them with modern designs incorporating the lessons of the Spanish Civil War and the Battle of Khalkhin Gol (Nomonhan). Some of these designs leapfrogged other countries' tank designs. The most significant was the T-34, originally designed as the successor to the BT series, but with its heavier armour and heavy dual-purpose gun it became the best medium tank of the first half of World War II. The T-34 eventually replaced almost all other Soviet tanks. The basic design was good enough to keep it battle-worthy beyond 1945, having been upgraded with heavier guns, new turrets and other modifications. The second significant design was the KV-1 tank. These were armed with the same excellent 76.2 mm gun as the T-34, and had the same V-2 diesel engine. However, the KV had a torsion bar suspension and much heavier armour than the T-34. The KV was slow, intended as a breakthrough tank. The KV-2 close-support version was armed with a 152 mm howitzer. The KV series was the main Soviet heavy tank until 1943, when production ended and most had been expended. Early in 1944 the KV's successor was the IS-2, armed with a 122 mm gun, having thicker armour and better mobility. The new infantry-support tank of 1941, intended to be the replacement for the T-26, was the T-50, armed with a 45 mm gun, with torsion-bar suspension and excellent armour for its class. Production problems with its new engine led to the tank being cancelled after less than 70 had been made. Finally, the light reconnaissance role was to be filled by the amphibious T-40 and the cheaper non-amphibious T-60.
At the beginning of Germany's Operation Barbarossa most of the Soviet Union's tank forces were composed of the T-26 tank series and BT. A few T-40s had appeared, along with about 1363 mechanically unreliable early T-34 tanks, and 677 KV-1 and KV-2s. Many early T-34s were captured or destroyed. Much of this early failure was due to lack of coordination, ill-supplied and ill-trained tank crews, and the lack of readiness of the Red Army in general. Another difficulty for the T-34 was that it had only a four man crew, with the tank commander doubling as the gunner. Although spared from loading duties, as French tank commanders had been, it still crippled the tank commander's ability to maintain awareness of the battlefield while firing the tank's main gun, giving a tactical advantage to German armour.
In 1941 great numbers of T-60s appeared, supplemented in 1942 with the similar T-70. Both light tanks had torsion-bar suspension, light armour, and small truck engines. Their simple construction kept them in production even though their combat value was limited. The T-60 had only a 20 mm gun while the T-70 had a 45 mm. However, both had one-man turrets, making them difficult to crew effectively. The T-70 formed the basis for the much more important self-propelled gun SU-76 later in the war.
By October 1942 Life magazine wrote, "The best tanks in the world today are probably the Russian tanks...". The T-34 effectively made all German tanks produced to that date obsolete. In fact, at its height the T-34 was deemed so successful, and so capable in every role, that production of all other tanks except the IS-2 was stopped to allow all available resources to be used exclusively for this tank. The T-34 forced the Germans to adopt new, heavier designs such as the Panther and Tiger, which in turn forced upgrades to the Soviet, United States and British tank fleets. Perhaps more significantly to the ultimate course of the war, the move to more complex and expensive German tank designs overwhelmed the already critically strained German tank-production capability, reducing the numbers of tanks available to German forces and thus helping to force Germany to surrender the initiative in the war to the Allies.
Later in the war the light tank role was increasingly filled by Lend-Lease supplies of United States M-3 light tanks and British and Canadian-built Valentine tanks. Ironically, the T-34 was as fast or faster than many of the light tanks that were supposed to scout for it, further encouraging reductions in Soviet light tank production.
In response to better German tanks, the Soviets began to produce the T-34-85 in the winter of 1943-44. This model had a much larger turret mounting an 85-mm gun and a 3-man turret crew, finally allowing the tank commander to concentrate fully on maintaining tactical awareness of the battlefield. The Soviets also responded with the 122 mm-armed IS-2 heavy tank, which carried heavier armour than the KV without an increase in overall weight; this was achieved by thinning the rear armour and moving most of the armour to the front of the tank, where it was expected to take most of its hits.
The IS-3 variant, produced in mid-1945, had a much more streamlined look and a larger, bowl-shaped tapered turret. Remarkably, the IS-3 had thicker armour but actually weighed slightly less than the IS-2, remaining under 50 tons (as compared to the Tiger II's 68). The armour design of the IS-3 was an enormous influence on postwar tank design, as seen in the Soviet T-55 and T-62 series, the United States M48 and the Federal German Leopard.
Soviet tank production outstripped all other nations with the exception of the United States. The Soviets accomplished this through standardization on a few designs, generally forgoing minor qualitative improvements and changing designs only when upgrades would result in a major improvement.
United Kingdom 
Britain had been the worldwide trend-setter in tank development from 1915, but had lost its leadership position as the war approached. Hampered by restricted expenditure in the years leading up the war and still organised for operations in Imperial defence as an expeditionary force, the British Army entered the war unprepared for the very sort of war its influential theorists such as J.F.C. Fuller and B. H. Liddell Hart had advocated.
The British Army had two types of tanks - "Infantry Tanks" which were heavily armoured with good all terrain performance but were slow. This lack of speed was not considered a flaw as they were designed to support infantry assaults on enemy strong points or urban warfare where the ability to outpace a man on foot was deemed unnecessary. The other type were "Cruiser Tanks" which were intended for independent maneuvering, rapid breakouts and flanking attacks. Early Cruiser tanks gained performance at a cost in the armour they could carry. Reliability was an important issue especially in the harsh conditions of North Africa and the mountainous terrain of Southern Europe, where the A10 and A13 in particular picked up reputations for broken track and overheating engines.
British crews were trained to fire on the move and the armament was mounted for optimum balance such that the gunner could aim with his body rather than use geared elevation. This reduced available space inside the turret. Both early Cruiser and Infantry tanks carried the QF 2pdr, a 40 mm caliber anti-tank gun, a good match for the contemporary German 3.7 cm KwK 36, and effective against tanks of the time but increasingly outclassed as the war progressed. Production shortages caused by losses in France and the Battle of the Atlantic forced the British to delay widespread introduction of the 6-pdr (57 mm) anti-tank gun until 1942. The lack of an adequate HE shell for the 2-pdr and the growing number of 50mm KwK 38 anti-tank guns in the Afrika Korps gave the German army in Libya a huge advantage for much of late 1941 and early 1942. This began to be off set by late 1942 but the Wehrmacht continued to enjoy an 12-18 month lead in tank and anti-tank gun development and production until the end of 1944.
The A9 Cruiser Mk I was an effective tank in the French, Greek and early North African campaigns. The 2 pdr gun was better than comparable 37 mm weapons of Germany and US, and lethal against tanks encountered during the North African campaign. However the minimal armor made the A9 an easy kill for most German anti-tank weapons.
A number of A10 Cruiser Mark IIs were part of the British Expeditionary Force (BEF) sent to France in the early stages of World War II. The A10's cross country performance was recorded as poor, but they were still used later in North Africa at the defence of Tobruk in 1941, where reliability and suspension performance in the desert conditions was praised. Sixty worn out examples were taken to Greece, by the 3rd Royal Tank Regiment and although they performed well against the German tanks, over 90% were lost due to mechanical breakdowns as opposed to enemy action (mainly through broken tracks).
As war broke out, the British had placed into production the A13, a new faster Cruiser tank utilizing the suspension and running gear concepts of the American designer J. Walter Christie. This new suspension provided a fast, highly maneuverable design that became the basis for the rapid evolution of the Cruiser tank. The A13 Christie was developed into the A15 Crusader then the A27 Cromwell. The use of the powerful Rolls Royce Meteor engine, derived from the Rolls Royce Merlin, gave the Cromwell high speed and mobility. The final British cruiser design to see service was the A34 Comet; a development of the Cromwell, it carried a high velocity 77mm gun derived from the 17 pdr anti-tank gun; one of the most effective Allied anti-tank guns of WWII.
Beginning about mid-1942, many British tank units were equipped with vehicles supplied under lend-lease from the United States, such as the Stuart light tank, the Lee (or the British specification Grant variant thereof) and the Lee's/Grant's replacement the Sherman. In late 1943, the British found a way to mount the 17 pdr anti-tank gun to the Sherman to create the Firefly, a tank with a more capable gun than the 75mm or 76mm gun normally fitted. From mid-1944, as more were produced and British designs were introduced into service the Firefly became increasingly the most common Sherman in use by the British.
Specialist Tanks 
Immediately before and during the war, the British produced an enormous array of prototype tanks and modified tanks for a variety of specialist engineering tasks (such as the Hobart's Funnies produced for the invasion of France in 1944).
For example, the Churchill Armoured Vehicle Royal Engineers fired a short range 290 mm (11.4 inch) direct-fire mortar which was used for destroying buildings and clearing obstacles. It could also be equipped with a wide variety of combat engineering equipment such as small bridges, rolled-matt roadways, fascines, and mine rollers.
Many of the these ideas had already been tried, tested or were in experimental development both by Britain and other nations. For example, the Scorpion flail tank (a modified Matilda tank) had already been used during the North African campaign to clear paths through German minefields. Soviet T-34 tanks had been modified with mine-rollers, fascines and flamethrowers. Close-support tanks, bridgelayers, and fascine carriers had been developed elsewhere also. However, the Funnies were the largest and most elaborate collection of engineering vehicles available.
By early 1944, Hobart could demonstrate to Eisenhower and Montgomery a brigade each of swimming DD tanks, Crab mine clearers, and AVRE (Engineer) tanks along with a regiment of Crocodile flamethrowing tanks.
United States 
Prior to the entry of the United States in the war after the attack on Pearl Harbor in December 1941, the Army had only a few tanks. During the Louisiana Maneuvers in September 1941, it used trucks with the word "tank" painted on their side.
The Light Tank M2 series was the most important pre-war US tank. These light tanks were mechanically very reliable, with good mobility. However, they had a high silhouette and poor armor. Only a few saw combat, on Guadalcanal. Their importance lies in the fact that they formed the basis for the much more successful Light Tank M3 series beginning in 1941. The Stuart was an improvement of the M2, with heavier armor and a 37 mm gun. From the M3A1 version, this gun was gyrostabilized.
The new medium tank just entering production in 1940 was the M2 series. This was a poor design with thin armour, a high silhouette, a 37 mm main gun and seven machine guns.
From 1940, new tank designs were prepared. The Battle of France had shown the importance of medium tanks. The British Army sought to have the US manufacture British designs, but the US refused, offering instead to share the output of US factories building US designs. The United States Army had a requirement for a medium tank with a 75 mm gun, and developed the M3 Medium Tank as an interim design. The M3 medium was intended to quickly get a 75mm gun into the field, pending the design of a tank with a 75mm gun in a fully rotating turret. The British immediately ordered the M3 for their own use with modifications to their requirements.
By February 1942, American civilian automobile factories only made weapons and military vehicles. Automobile manufacturers such as General Motors and Chrysler used their experience with mass production to quickly build tanks. The country manufactured as many tanks in the first half of 1942 than in all of 1941, with 1,500 in May 1942 alone. American production equipped not only its forces, but through Lend Lease also supplied all the tank needs of the free French (after 1942) and Chinese. By 1944 most British units were also equipped with US-built tanks. Finally, the US supplied over 8,000 tanks to the USSR, half of them the M4 Sherman. Similarly to the Soviet Union, the United States selected a few good basic designs and standardized on those models. Given the lack of tank design and production experience, it is remarkable that the United States designs were as good as they were.
The first tanks of the United States to see combat were the Light Tank M3. They were deeply flawed in many ways, yet the M3 light ("Stuart") and M3 medium ("Lee" or "Grant") were the best tanks available to the Western Allies and were superior to many of their German counterparts in armour protection and firepower. The Light Tank M3 was about as well-armed as the (2 pdr-armed) British cruiser tanks in the desert, yet was much more reliable mechanically. Its 37 mm main gun was more powerful than the main guns carried by German reconnaissance tanks. The name given by the British to the Light Tank M3 was 'Stuart'; a nickname used was 'Honey'. The M3 and its improved derivative, the Light Tank M5 series, remained in service throughout the war. By 1943, its 37 mm gun made it a very dangerous tank to serve in, but no better replacement was available. The Light Tank T7 design was proposed as a successor in 1943, armed with a 57 mm gun and with better armour; however, the design was never standardized for production.
The appearance of the M3 Lee medium tank in the summer of 1942 finally gave the British a larger supply of medium tanks than they could otherwise have hoped for. Although poorly designed, with a very high profile, it was produced in great numbers and was very effective when engaging targets other than enemy tanks, such infantry and gun positions.
The M3 had the significant disadvantage of its 75 mm main armament being mounted offset in the hull. It had a fully traversable turret with a 37 mm cannon as well, but the turret combined with a hull gun gave it a very tall profile. The United States 1st Armored Division also employed the M3 in Africa. It was a stopgap solution, never intended to be a design of major importance. In American and British service the M3 medium was phased out at the end of the North African campaign. It continued to serve in the Red Army for some time, and in a single campaign in the Pacific. Red Army crews nicknamed it "grave for seven brothers" referring to the seven-man crew.
The most important American design of the war was the M4 Sherman medium tank. The M4 became the second-most-produced tank of World War II, and was the only tank to be used by virtually all Allied forces (thanks to the American lend-lease program); approximately 40,000 M4 Shermans were produced during the war. M4s formed the main tank of American, British, Canadian, French, Polish and Chinese units. The M4 was the equal of the German medium tanks, the Panzer III and Panzer IV, at the time it first saw service in 1942. The Red Army was supplied with about 4,000 M4s. The M4, although reliable and easy to maintain, was already outgunned by the time the US encountered the up-gunned and up-armoured German medium tanks in Italy and Northern Europe (the Panzer IV and various German self-propelled guns) and by late 1943 the arrival of German Panther and Tiger I were even graver threats due to the range, accuracy and penetrating power of their main guns. While it is commonly believed that the Sherman had a tendency to explode catastrophically due to their use of petrol, this is incorrect. The Sherman suffered from thin armour and poor ammunition storage. Welded-on applique armour & water jackets were added to combat the problem. A U.S. Army study in 1945 concluded that 60–80 percent of the older dry-stowage & 10–15 percent of wet-stowage Shermans burned when penetrated.
The Sherman gained grim nicknames such as "Tommycooker" from the Germans, who called British soldiers "Tommies". The British and Canadians called the Sherman the "Ronson" after the Ronson cigarette lighter which had the slogan "Lights up the first time, every time!".
Flawed United States armour doctrine played a major role in keeping the M4 undergunned in 1944-1945. This doctrine emphasized that tanks were to be used primarily for infantry support and exploitation, while the role of fighting enemy tanks was to be carried out by the tank destroyer branch, armed with both towed and self-propelled guns such as the 3 inch Gun Motor Carriage M10. The 3" GMC M10 was thinly armoured, with an open-topped turret mounting a 3-inch gun that was very powerful by mid-war standards.
Technically, the M4's design was capable of handling larger guns than the 75 mm and 76 mm guns with which they left the factory. The British fitted Shermans with the more powerful Ordnance Quick Firing 17 pounder gun, a variant known informally as the Firefly.
By the time of the Normandy campaign, the M4 had become the workhorse tank of the Allied forces. Some Shermans were equipped with the Duplex Drive system (Sherman DD), which allowed them to swim using a collapsible screen and inflated rubber tubes. Along with this were the M1 Dozer Blade (a Sherman with a bulldozer blade),the Sherman T34 (which had a multiple rocket launcher installed above the turret), the POA-CWS-H5 (a Sherman with a flame-thrower), and the Sherman Crab Mark I (a Sherman with a mine flail), as well as many other variants.
The United States eventually deployed the Light Tank M24, an improvement over the M3 light tank. The M24 had torsion-bar suspension, high mobility, and a compact 75 mm gun. Ergonomically the tank was quite good also. However, the M24 did not appear in combat until December 1944 and equipped only a few units by the end of the war.
Near the end of the war the M26 Pershing heavy tank was deployed operationally. The Pershing was a very modern design with torsion-bar suspension, heavy armor, and an excellent 90 mm gun. However, it was somewhat underpowered, having the same Ford GAA engine as the M4A3. The M26 basic design was good enough to form the basis for all postwar American tanks through the end of the M60 series.
At the start of the war, France had one of the largest tank forces in the world along with the Soviet, British and German forces. Like the British and the Soviets, the French operated two classes of tank: cavalry tanks and infantry tanks.
The French had planned for a defensive war and built tanks accordingly. Their infantry tanks were heavily armoured. But operationally in terms of control of their forces, the French were at a disadvantage and were outmaneuvered by the German forces. When the French were able to mount an attack their tanks could be very effective. On 16 May, during the Battle of France a single Char B1 heavy tank, the Eure, attacked and destroyed thirteen German tanks lying in ambush in Stonne, all of them Panzer IIIs and Panzer IVs, in the course of a few minutes. The tank safely returned despite being hit 140 times (this event is not verifiable in German documents and relies on the statements of the crew). In his book Panzer Leader, Heinz Guderian wrote of a tank battle south of Juniville: "While the tank battle was in progress, I attempted, in vain, to destroy a Char B with a captured 47 mm anti-tank gun; all the shells I fired at it simply bounced harmlessly off its thick armor. Our 37 mm and 20 mm guns were equally ineffective against this adversary. As a result, we inevitably suffered sadly heavy casualties".
The total tank assets in France and its colonies were perhaps less than 5,800 during the time of the German offensive. After the armistice in the unoccupied Free Zone of France a clandestine rebuild took place of 225 GMC Trucks into armoured cars. When all of France was occupied in 1942 the secret hiding places were betrayed to the Germans.
Germany's armoured (panzer) force was not especially impressive from a technical standpoint at the start of the war. As noted above, it was their advanced combined arms doctrine and unrivalled command-and-control capability that gave German mechanized forces their advantage on the battlefield.
Pre-war plans called for two main tanks: the main tank was to be the Panzer III medium tank, supported by smaller numbers of the howitzer-armed Panzer IV. However, by the beginning of the invasion of Poland, only a few hundred of these vehicles were available. As a result, the invasions of Poland and France were carried out primarily with the less capable Panzer I and Panzer II light tanks, with some cannon-armed light tanks from Czechoslovakia. Even in 1941, Panzer III production amounted only to about 1,000 tanks, forcing the Germans to use Czech tanks as substitutes for the Panzer III. As the war proceeded, production of heavier tanks increased.
The Panzer III was intended to fight other tanks; in the initial design stage a 50 mm (2 inch) gun was specified. However, the infantry at the time were being equipped with the 37 mm (1.46 inch) PaK 36, and it was thought that in the interest of standardization the tanks should carry the same armament. As a compromise, the turret ring was made large enough to accommodate a 50 mm (2 inch) gun should a future upgrade be required. This single decision later assured the Panzer III a prolonged life in the German army. The Panzer IV was intended to carry a gun that could be used in support of infantry or other tanks, and was initially armed with a short-barreled 75 mm howitzer to fire high explosive content (HE) fragmentation shells. In 1941 an average of 39 Panzer IV models tanks per month were built, and this rose to 83 in 1942, 252 in 1943, and 300 in 1944.
During Operation Barbarossa, the German invasion of the Soviet Union in 1941, it was discovered that the Soviet T-34 tank outclassed the Panzer III and IV. Its sloped armour could withstand most German weapons, and its 76.2 mm gun could penetrate the armour of all German tanks. This forced the Germans to improve their existing models. The Panzer III, which was intended to be the main medium tank, was upgraded to a longer, higher-velocity 50 mm gun.
Thus the Panzer IV, originally intended to be a support tank, became the de facto main medium tank re-armed with a long-barrelled, high velocity 75 mm gun to counter the T-34; the Panzer III, with its smaller turret ring, could not mount a gun larger than 50mm, which had become inadequate against Allied tanks.
The Germans also started to develop newer, heavier tanks. This included the Panzer V Panther, which was intended to be the new main German medium tank. The Panther tank was a compromise of various requirements. While sharing essentially the same engine as the Tiger I tank, it had better frontal armor, better gun penetration, was lighter overall and thus faster, and could handle rough terrain better than the Tigers. The tradeoff was much weaker side armor; the Panther proved to be deadly in open country and shooting from long range, but vulnerable to close-quarters combat or flank shots.
The Germans also started to develop a new series of heavy tanks. The first was the Tiger, which outclassed all its opponents in terms of firepower and armour when it was first put into operational use. The even heavier Tiger II supplemented the Tiger I late in the war. Its powerful gun and very heavy armor made it superior to every Allied or Soviet tank in a one-on-one confrontation, but the poor mobility and reliability limited its use. Plans were made for even heavier tanks, such as the Panzer VIII Maus, but only prototypes were produced.
Tanks of Other Combatants 
By the time of the Sudeten crisis, Czechoslovak army used a complement of light tanks including 298 LT vz. 35 designed by Škoda, as well as 50 LT vz. 34 built by ČKD; 150 LT vz. 38 were ordered but none were delivered before the German occupation. The LT-35 and LT-38 models were superior to the Panzer I and Panzer II light tanks used in the Wehrmacht, so the Germans ordered to resume the production of these models.
Before the end of production in 1942, 136 more LT-35 and a total of 1414 LT-38 were produced for the Wehrmacht at Škoda Works; these tanks saw operational use in the Polish campaign, the Battle of France, and on the Soviet front. By 1942, Czech-built tanks became progressively vulnerable to Soviet T-34 medium tanks and new anti-tank cannons. Moreover, LT-35 and LT-38 proved unsuitable for harsh winter conditions in Russia, so they were withdrawn from front line service in 1942; the remaining units were either redeployed in a light reconnaissance role, or converted to Hetzer tank destroyers and artillery tractors.
The Italian army was mainly equipped with tankettes of the L3 series in the 1930s, and these formed the main armour strength of Italy as late as 1940.
Italy began fielding heavier tanks beginning with the M-11/39 of 1940. The M-11/39 and its successors, the M-13-14-15 series, were designated medium tanks by the Italians, but in fact were closely comparable in combat power to light tanks such as the Soviet T-26.
A single "heavy" tank, the P40, was designed, but none saw service with Italian forces. The few produced after the Italian surrender were used by the Germans. The P40 design had firepower comparable to Allied and German medium tanks but was far lighter and thus less well armoured.
The Fiat-Ansaldo M11/39 medium tank was used from 1940 through the early period of World War II. The M11/39 was developed as a "breakthrough tank" (Carro di Rottura). It was replaced by the Fiat-Ansaldo M13/40 a medium tank ("M" for Medio (medium) according to the Italian tank weight standards at the time: 13 tonnes was the scheduled weight and 1940 the initial year of production), in the Italian Army and was used in the Greek campaign in 1940 and 1941 and in the North African Campaign.
The M13/40 was not used on the Eastern Front; Italian forces there were equipped only with Fiat L6/40s and Semovente 47/32s. Armament was sufficient for 1940-41 but did not keep up with the increased armour and firepower on Allied or German tanks. Beginning in 1942, the Italian Army recognized the firepower weakness of the M13/40 series and employed the Semovente 75/18 self-propelled gun alongside the tanks in their armoured units.
The next tank in the series was the Fiat M14/41, a slightly improved version of the M13/40 with a more powerful diesel engine. The tank was also employed in the North African Campaign. The vehicle was unreliable, cramped, and caught fire easily when hit. Following the withdrawal of Italian forces from North Africa the M14/41 was rarely encountered. A few captured M-11, M-13 and M-14s were pressed into service by British and Australian forces to fill the serious shortage of allied tanks in 1941.
The next in the series was the M15/42, a 15 tonne tank first built in January 1943. Some 90 vehicles were built before the Italian armistice in September 1943 and in connection to that event they were used in battle against the Germans by the Ariete armored division in Rome. After that point they were confiscated and used by the Germans who also built another 28 M15/42 tanks. It had a more powerful engine and air filters to cope with the harsh conditions of the desert, and a slightly improved version of the 47mm gun.
Like the US Army (which utilized French and British tanks in World War I), the Imperial Japanese Army (IJA) did not have tanks of its own in World War I, so it started out by purchasing foreign tanks for evaluation during World War I, and then began developing its own designs. Like many other nations, the Japanese initially didn't embrace the tank, as it didn't have the cavalry tradition. Cavalry was used for reconnaissance in the mountainous countryside, and initially, as with most other armies, the first designs were constrained by the tank's infantry support role. Inspired by European designs, the Japanese tank program designed and developed the tanks which facilitated their campaigns in China and Nomonhan against the Soviet Union, prior to WWII. They introduced many innovations as they built their designs, including bell-crank suspensions, were pioneers in amphibious tanks, and the use of diesel engines as they were less likely to catch on fire versus the regular gas engines that were being used at the time. The Japanese Generals had made a mistake in their assessment of the tanks used against China, a country whose army had only three tank battalions, and few antitank weapons.
By 1937, Japan fielded 1,060 tanks in 8 regiments, most designed for and used in the infantry support role. But this focus left the IJA without a tank capable of taking on other tanks, a deficiency that was brought home hard during the battle of Khalkin-Gol (also known as Nomonhan), a decisive defeat inflicted by the Russians on the Mongolian border in 1939. This proved fatal later when they faced the new generation of Allied tanks, as the great majority of the Japanese models were lightly armored, and not heavily gunned. With the priority of steel being consumed by the Imperial Japanese Navy and Air Force, the Japanese Army was relegated the remaining material for its tanks. Thus the 1930s designed vehicles went on being mass-produced, and the warning of Khalkin-Gol was too slowly recognized. By 1940 they had the fifth largest tank force in the world behind the Soviet Union, France, Britain and Germany, but were behind in medium and heavy tanks. After 1941, with the new focus on building warships and aircraft, and with the entry of the United States into the conflict, priorities shifted to weapons that were more conducive to naval warfare; attacking across the Pacific, and defending the Empire from the advancing Americans.
So although the Japanese Army deployed approximately 200 tanks to the Pacific Theater of Operations, the tanks that Allied forces in the Pacific faced were primarily designs of the 1930s, such as the Type 97 medium and Type 95 light tanks. Even so, these tanks were often delayed by shortages of raw materials, and even after arriving off of the assembly lines doctrine called for them to be held for the defense of the mainland, and not dispersed to the far flung Imperial Japanese Army or Navy forces. The Japanese built tanks to match up against the Allied tanks, such as the Type 2 Ho-I Infantry Support Tank with a 75 mm gun designed as a self-propelled howitzer or tank destroyer for the close fire support role, to provide Type 97 Chi-Ha equipped Japanese tank regiments with additional firepower against enemy armored fighting vehicles, but in limited amounts. Between 1931 and 1945, Japan produced 6450 tanks. Half of them (3300) were made by the Mitsubishi Company. The sub-total of tanks produced between 1940 and 1945 is 4424, i.e. a yearly average comparable to Italy. For a country as large and as industrialized as Japan, that is modest. Before 1945, the fleet and the air force had priority. It changed when the homeland went under direct threat but it was too late.
Poland was the first to suffer the German Blitzkrieg, but it had some very good tanks in its amoured forces. The most important was the 7TP (siedmiotonowy polski - "7-tonne Polish") light tank, which was better armed than its most common opponents, the German Panzer I and Panzer II.
Like the similar Soviet T-26, the 7TP was a development of the British Vickers 6-ton (Mk.E) which the Poles purchased and licensed for local production. The main new features of 7TP were: a better, more reliable and powerful diesel engine (which made the 7TP world's first diesel tank), 37 mm anti-tank gun, and slightly thicker armour (17 mm in front instead of 13 mm). Only about 132 tanks were produced between 1935 and the outbreak of the war. The weight increased after the initial 7-tonne prototype was made and the actual serial tanks weighed approximately 9 tonnes.
Like its British predecessor, the 7TP was initially produced in two variants: the twin turret version armed with 2 Ckm wz.30 machine guns, and a single turret version, armed with a 37 mm Bofors wz. 37 gun. After initial tests, it became clear that the twin-turret variant was obsolete and lacked firepower, so it was abandoned in favour of the more modern single turret design.
Poland also had the TK (also known as the TK-3) tankette which was based upon an improved chassis of the British Carden Loyd tankette. The 575 TK/TKS tankettes formed the bulk of the Polish armoured forces but with armament limited to machineguns, their combat value was limited. They suffered heavy losses during the Invasion of Poland. Only the handful of tankettes armed with 20 mm guns had a fighting chance against the enemy tanks; in one instance on 18 September 1939 a 20 mm gunned TKS destroyed three German Panzerkampfwagen 35(t) tanks.
All of the 7TP tanks took part in combat in the Polish Defensive War of 1939. Most of them were attached to two light tank battalions (the 1st and the 2nd).
Polish forces in exile after the fall of Poland were reequipped by their allies. Polish LWP forces fighting alongside the Red Army were equipped with T-34, T-70 and IS-2 tanks, along with ISU-122 and SU-76 self-propelled guns. Polish forces in the west were equipped out of British stocks including M3 and M5 Stuarts, M4 Shermans and a small number of Cromwells. Polish armour units were participants in the Battle of Berlin and played an important role in the campaign in Normandy.
See also 
- History of the tank
- Tanks in World War I
- Comparison of World War I tanks
- List of interwar armoured fighting vehicles
- Comparison of early World War II tanks
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US Army tests Normandy 1944