Tanks were an important weapons system in World War II. Although tanks in the inter-war years were the subject of widespread research, few were made in just a few countries. However, during World War II, most armies employed tanks, and thousands were built every month. Tank usage, doctrine, and production varied widely among the combatant nations. By war's end, a consensus was forming on tank doctrine and design.
Background
The tank was invented by the British, in 1916, and first used during 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. World War I tanks moved at a walking pace, they were relatively unreliable, and the best usage of them was still developing up to the war's end. A breakthrough in tank design was the Christie suspension, developed by an American engineer, J. Walter Christie, which allowed longer movement of the suspension than conventional leaf-spring systems then in common use, and allowed the tanks to move faster.
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 were adapted to combat engineering roles.
Tank design gradually improved in the inter-war period also. Reflecting the growth of the automotive industry, tank engines, transmissions, and track systems were improved. By the beginning of the war in September 1939, tanks were available that could travel hundreds of miles on their tracks with a limited number of breakdowns.
The war accelerated the pace of change in design. In particular, the gun-vs-armor race of the war led to rapid improvements in firepower and armor.
Major themes
The United Kingdom, the US, the Soviet Union, and France produced significant numbers of tanks before and during World War II. The early tanks of Germany were inferior to many of their opponents' tanks in the areas of armor and firepower. However, in their tactical employment the German tanks dominated all rivals early in the war. Germany concentrated the tanks and the few infantry transport vehicles it had into Panzer divisions. German doctrine stressed the use of rapid movement, mission-type tactics and combined-arms where tanks operated with mobile infantry and air support; this doctrine was popularly called [a] Blitzkrieg. For this to work the German tanks were all equipped 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 armor in the 1940 campaign, but their poor command and control doctrine negated these advantages. By 1943, two-way radio was nearly universal in all armies.
A trend towards heavier tanks was unmistakable as the war proceeded. In 1939, most tanks had maximum armor of or less, with guns with no larger caliber than 37–47 mm. Medium tanks of 1939 weighed around . By 1945, typical medium tanks had maximum armor over 60 mm thick, with guns in the range and weights of . Light tanks, which dominated most armies early in the war, gradually disappeared from front-line service.
Turrets, which had always been considered, but were not previously a universal feature on tanks, became recognized as essential. It was appreciated that if the tank's gun was to be used to engage both 'soft' (unarmored) and armored 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 hull down 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 (hull mounted and turret gun), French Char B1 (hull mounted howitzer) or British Cruiser Mk I (two ancillary machine gun turrets) slowly became less common during World War II. Experience showed that a tank commander could not effectively direct the fire of several weapons; also, the newer dual-purpose guns eliminated the need for multiple weapons. Most tanks still retained a hull machine gun, and usually one or more machine guns in the turret, to protect them from infantry at short range.
Tanks were adapted to a wide range of military tasks, including engineering. Specialized models, such as flame-thrower tanks, armored recovery vehicles for towing disabled tanks from the battlefield, and command tanks with extra radios were also used. Some of these tank variants live on as other classes of armored fighting vehicle, no longer called "tanks". All major combatant powers also developed tank destroyers (self-propelled anti-tank guns for mobile defense) and assault guns, as armored vehicles carrying large-caliber guns, but often no turrets. Turreted vehicles are expensive to manufacture compared to non-turreted vehicles.
One trend seen in World War II was the usage of older, lighter tank chassis to mount larger weapons in fixed casemates, as self-propelled guns, 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 such as the SU-100, the successor of the SU-85. 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.
The German tank destroyers Panzerjäger ("tank hunters") were basically made by taking an existing anti-tank gun and mounting it on a convenient chassis to give mobility, usually with just a three-sided gun shield for crew protection. For instance, 202 obsolete Panzer I light tanks were modified by removing the turret and emplacing a Czech 4,7cm KPÚV vz. 38 (47 mm) anti-tank gun giving the Panzerjäger I self-propelled anti-tank gun. German tank destroyers based on the Panzer III and later German tanks were unique in that they had more armor than their tank counterparts.
Fully enclosed casemates on the Germans' Sturmgeschütz assault guns, from the beginning of the war, set a pattern used later by the similarly fully enclosed Jagdpanzer casemate-style tank destroyers, with the Soviets' similar Samokhodnaya ustanovka (SU) assault guns being used for the same dual-purpose roles. However, the lack of a rotating turret had limited the gun's traverse to a few degrees. This meant that the entire tank normally had to be turned onto its target by the driver, a much slower process than simply rotating a powered turret. If the vehicle became immobilized due to engine failure or track damage, it could not rotate its gun to counter opposing tanks, making it highly vulnerable to counterfire.Irwin, John P. Another River, Another Town, New York: Random House Publishers (2002), p. 61. This vulnerability was later exploited by opposing tank forces. Even the largest and most powerful of German tank destroyers were found abandoned on the field after a battle, having been immobilized by one or more hits by high explosive (HE) or armor-piercing (AP) shells to the track or front drive sprocket.Irwin, p. 62: Even the U.S. M4 Sherman could disable a Jagdpanther's track or fracture the front drive sprocket with a 75 mm HE shell.
Tank development timeline
Tanks of the major combatants
Soviet Union
The Soviet Union started 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 T-26 (derived from the Vickers 6-ton), lightly armoured and armed with a 45 mm anti-tank gun M1932 (19-K) gun 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 at the time. 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 reconnaissance tanks such as the amphibious T-37 and T-38 tanks. 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, multi-turreted tanks, which were in most respects equal to the German Panzer IV. Again, though, this design dated from 1931 and was obsolete.
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 of the officer class. By 1940, the Red Army had adopted an advanced combat doctrine that its command structure and tank force simply could not execute.
Several excellent designs began production in 1940–1941. Just prior to the war, the Red Army embarked on two closely related projects to reorganize its mechanized forces and re-equip them with modern designs that took lessons learned from the Spanish Civil War, the Battle of Khalkhin Gol and the Winter War into account. Some of these designs were copies of other countries' designs. The most significant was the T-34, which was originally designed as the successor to the BT series. Its heavier armour and 76.2 mm dual-purpose gun made it one of the best medium tanks of the first half of World War II. The T-34 eventually took on the roles of many other Soviet tanks. The T-34's chassis made it usable after the war, as it could be continuously upgraded with heavier guns, new turrets and other modifications. The other significant design was the KV-1 tank. These were armed with the same 76.2 mm gun as the T-34, and had the same Kharkiv model V-2 diesel engine. The KV tanks were equipped with 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 howitzer. The KV series was the main Soviet heavy tank until 1943, with the end of production and the destruction of most surviving vehicles. Early in 1944, the KV's successor, the IS-2 was introduced. It was armed with a gun, with thicker armour and better mobility. A new infantry-support tank was introduced in 1941: the T-50. It was intended to be the replacement for the T-26, and was equipped with a 45 mm gun, torsion-bar suspension and thicker armor than most other tanks in its class. However, production problems with its new engine led to the tank being cancelled after fewer than 70 had been made. The light reconnaissance role was filled by the amphibious T-40 and the cheaper, non-amphibious T-60.