Tank development both evolved considerably from World War II and played a key role during the Cold War (1947–1991). The period pitted the nations of the Eastern Bloc (organized under the Warsaw Pact in 1955) and the North Atlantic Treaty Organization (NATO) (since 1949) against each other.

After World War II, tank design budgets were cut and engineering staff was often scattered. Many war planners believed that with the advent of nuclear weapons the tank was obsolete, given that a tactical nuclear weapon could destroy any brigade or regiment, whether it was armoured or not.

In spite of this, tanks would not only continue to be produced in huge numbers, but the technology advanced dramatically as well. Tanks became larger and advances in armour made it much more effective. Aspects of gun technology changed significantly as well, with advances in shell design and terminal effectiveness.

Soviet domination of the Warsaw Pact led to effective standardization on a few tank designs. Oppositely, the key NATO nations – the US, UK, France, and West Germany – all developed their own tank designs. These had little in common, with smaller NATO nations purchasing or adapting one or more of these designs.

The Korean War proved that tanks were still useful on the battlefield, given the hesitation of the great powers to use nuclear weapons. In the 1950s, many nations' tanks were equipped with NBC (nuclear, biologic, and chemical) protection, allowing mechanized units to defend against all three types of weapon, or to conduct breakthroughs by exploiting battlefield nuclear strikes.

The decades since have seen continual improvements in tank design, but no fundamental change. Among these have been larger yet guns, correspondingly improved armor systems, and refinements to targeting and ranging (fire control), gun stabilisation, communications and crew comfort.

Transition to main battle tanks During and after World War II some medium tanks designs, such as the American M26 and Soviet T-44, were mass produced before the concept of a main battle tank idea had evolved. These were highly similar to early main battle tanks, with powerful guns, moderate armor, and decent mobility. Their successors, the M46 Patton and T-54, followed suit before the main battle tank doctrine was fully accepted.

Development of the main battle tank

Medium tanks gradually evolved into the new concept of the main battle tank. This transition happened gradually in the 1950s, as it was realized that medium tanks could carry guns (such as the US 90 mm gun, Soviet 100mm D-10 tank gun, and especially the British L7 105 mm gun) that could penetrate any practical level of armour at long range. The World War II concept of heavy tanks, armed with the most powerful guns and heaviest armour, became obsolete since they were just as vulnerable as other vehicles to the new medium tanks. Likewise, World War II had shown that lightly armed, lightly armoured tanks were of little value in most roles. Even reconnaissance vehicles had shown a trend towards heavier weight and greater firepower during World War II; speed was not a substitute for armor and firepower.

An increasing variety of anti-tank weapons and the perceived threat of a nuclear war prioritized the need for additional armor. The additional armour prompted the design of even more powerful guns. The main battle tank thus took on the role the British had once called the 'Universal tank', filling almost all battlefield roles. Typical main battle tanks were well armed and highly mobile, but cheap enough to be built in large numbers. The classic main battle tanks of the 1950s were the British Centurion, the Soviet T-55 series, and the US M46 through the M48 series, which saw continuous updates throughout the Cold war. For example, the Centurion began life with the highly effective 17-pounder (76.2 mm) gun, but was upgraded to 20 pounder (84 mm) and then 105 mm main armament by 1959, with improved fire control and new engines.

The Soviet T-55 started with a 100 mm gun, but has been upgraded with both 115 mm and 125 mm guns, much improved fire control systems, new engines, track, etc. The M46 series evolved through to the M60 series. The first Soviet main battle tank was the T-64T-64 manual ("Танк Т-64А. Техническое описание и инструкция по эксплуатации. 1984") state T-64 as "main battle" tank, while previous T-62 and T-55 (in corresponding military manuals, like "Танк Т-62. Руководство по материальной части и эксплуатации. 1968") stated as "medium" tanks while the first American MBT was the M60 combat tank.MIL-T-45308 state "Tank, Main Battle, 105MM Gun, M60", while MIL-T-45148 state "TANK, COMBAT, FULL-TRACKED, 90MM GUN, M48A2"

These vehicles and their derivatives formed the bulk of the armoured forces of NATO and the Warsaw Pact throughout the Cold War; many remain in use in the 21st century.

Light tanks

Light tanks, such as the Soviet PT-76, maintained limited roles such as amphibious reconnaissance, support of Airborne units, and in rapid intervention forces which were not expected to face enemy tanks. The US M551 Sheridan had similar strengths and weaknesses, but could also be airdropped, either by parachute or LAPES. The value of light tanks for scouting has been diminished greatly by helicopters, although many continued to be fielded. During the early Cold War the US wielded the more conventional M41 Walker Bulldog. From the mid-late Cold War Infantry Fighting Vehicles such as the Soviet BMP and US M2 Bradley to an extent replaced light tanks, being similar to the extent that they are lesser armed and armored but lighter and cheaper than main battle tanks. At the end of the Cold War light tank-like armored cars were designed such as the South African Rooikat and the Italian B1 Centauro which have seen service in the post-Cold War era.

Heavy tanks

Heavy tanks such as the T-10 continued to be developed and fielded along with medium tanks until the 1960s and 1970s, when the development of anti-tank guided missiles and powerful tank guns rendered them ineffective. The combination of large high-explosive anti-tank (HEAT) warheads, with a long effective range relative to a tank gun, and with high accuracy, meant that heavy tanks could no longer function in a stand-off, or overwatch role; much cheaper antitank guided missiles could fill this role as well. Medium tanks were just as vulnerable to the new missiles, but could be fielded in greater numbers and had higher battlefield mobility.

Development of antitank weapons and countermeasures

After the Yom Kippur War of 1973, when Israeli tanks were destroyed in large quantities by man-portable wire-guided missiles (ATGMs) fired by Egyptian infantry, concerns were raised on the vulnerability of tanks on the battlefield to antitank weapons. Subsequent analysis showed that Israeli forces had underestimated their opponents during the first phases of the war; their all-tank tactics ignored the newfound ability of Infantry armed with cheap AT weapons to stop tanks. Tactically, there was renewed recognition for the need for combined-arms tactics. This led to greater mechanization of Infantry and advanced artillery tactics and warheads. Tanks alone were vulnerable to Infantry, but a combined team of tanks, mechanized Infantry, and mechanized artillery could still win in the new environment.

In 1974, the United States initiated a program to modernise its existing tank fleet and start real mass production of the M60A1, and later the M60A3; at the same time the M1 was developed. Budgets for tank design and production picked up during the administration of president Ronald Reagan, following tensions between the United States and the Soviet Union.

In response to infantry-portable and vehicle-mounted ATGMS, ever more capable vehicle armour were developed. Spaced armour, composite, explosive reactive armour, and active protection systems—like the Russian Shtora, Drozd, and Arena—were added to old and new tanks. Despite these improvements the larger missiles remained highly effective against tanks.

Missile-armed tanks

During the latter half of the 20th century, some tanks were armed with ATGMs (Anti-Tank Guided Missiles) which could be launched through a smoothbore or (in the case of "Shillelagh") a rifled main gun barrel with a provision to prevent imparting "spin" to the missile. In the U.S., the M60A2, M551 Sheridan, and prototype MBT-70, with 152 mm barrel/launchers used the Shillelagh infrared-guided missile.

During WWII a few tanks designs such as the M4 Sherman were modified to carry unguided rockets on the turret in addition to their main gun. This concept was to a limited extent carried into the Cold War with ATGMs; examples include the French AMX-13 and the Swedish Strv 81 (the Swedish version of the British centurion), both modified to carry SS.11 missiles on the top and sides of the turret, respectively.

The MBT-70 was cancelled prior to production due to high cost, and superseded by the M1 Abrams, which used a conventional gun. The M551 and the M60A2 were widely considered disappointing due to problems of overall complexity, sensitive advanced electrical systems (some components of which involved the Shillelagh guidance system) and issues related to the conventional rounds with combustible cases, though the Sheridan would serve into the 1990s before finally being withdrawn. The M60A2's were eventually replaced by M60A3s using conventional 105 mm guns.

The Soviet Union put gun-launched missiles into service in the mid-1970s, which continue to be used in CIS forces. Tanks capable of firing gun-launched missiles in Russian service include the T-72, T-80, T-90, and upgraded T-55 (T-55AM2). Ukraine also employs missile-armed T-64, T-80, and T-84 tanks.

History

Korean War

In the Korean War M24 Chaffees were the first U.S. tanks to fight the North Korean T-34-85s. The Chaffee fared poorly against these much better-armed and armored medium tanks. Chaffees were more successful later in the war in their reconnaissance role, supported by heavier tanks such as the M4 Sherman, M26 Pershing, and M46 Patton.

The heavier but older Pershing was deemed unsatisfactory due to its inferior mobility, which was unsuitable for a medium tank role as it used the same engine that powered the much lighter M4 Sherman, and 1949, the upgraded M26 received a new power plant and a main gun with bore evacuator, and the M46 Patton designation. Less than a thousand were upgraded to M46 standard.

On 8 August 1950 the first M46 Pattons landed in South Korea. The tank proved superior to the much lighter North Korean T-34-85, which were encountered in relatively small numbers. By the end of 1950, 200 M46 Pattons had been fielded, forming about 15% of US tank strength in Korea; the balance of 1,326 tanks shipped to Korea during 1950 included 679 M4A3 Shermans, 309 M26 Pershings, and 138 M24 Chaffee light tanks.Steven J. Zaloga "M26/M46 Pershing Tank 1943–1953" pp.39-40 Subsequent shipments of M46 and M46A1 Pattons allowed all remaining M26 Pershings to be withdrawn during 1951, and most Sherman equipped units were also reequipped.Donald W Boose Jr."US Army Forces in the Korean War 1950-53" pp.52,75-86

By 1953 the M24 Chaffees were completely replaced by the M41 Walker Bulldog, which was rushed to the battlefield by the U.S. Army. The Walker Bulldog was too late to see combat during the Korean War.