This article deals with the history and development of American tanks from the end of World War II and during the Cold War.

Light tanks

M24 Chaffee

In the Korean War M24 Chaffees were the first U.S. tanks to fight the North Korean T-34-85s. The M24 fared poorly against the much better-armed and armored medium tanks. When the war began in June 1950, the four American infantry divisions on occupation duty in Japan had no medium tanks at all, having only one active tank company (equipped with M24 Chaffee light tanks) each. When these divisions were sent to Korea at the end of June 1950, they soon found that the 75 mm gun on the M24 could not penetrate the armor of North Korean T-34 tanks, which had no difficulty penetrating the M24's thin armor. M24s were more successful later in the war in their reconnaissance role, supported by heavier tanks.

M41 Walker Bulldog

The development of the M41 Walker Bulldog began in 1947 to replace the M24 Chaffee. The vehicle was designed to be air-transportable and carry heavier firepower provided by an advanced 76 mm gun. The M41 was an agile and well armed. On the other hand, it was noisy, fuel-hungry and heavy enough to cause problems with air transport.

The Walker Bulldog saw limited combat with the Army during the Korean War, but for the most part the conflict served as a testing ground to work out the tank's deficiencies, especially with its rangefinder. At the time, it was designated as the T-41, and was rushed to the battlefield even before its first test run. This was because the North Koreans were supplied with Soviet T-34 tanks, which were superior to the M-24. By 1961, 150 were delivered to the Japan Ground Self-Defense Force to supplement their Type 61 medium tanks.

T92 The T92 Light Tank was designed in the 1950s by Aircraft Armaments as an airborne/airdropped replacement for the much heavier M41 Walker Bulldog. The main gun was a 76 mm cannon on a low profile turret. It had a crew of four with a semi-automatic loading system. Study of the Soviet PT-76 led to a new swimming requirement for light tanks, for which the design could not be modified, and thus the T-92 was never used.

M551 Sheridan

Plans started to build an even lighter replacement mounting the same gun, resulting in the T-71 and T-92 test designs. Two prototypes of the 19 ton T-92 were ordered. However, as the prototypes were entering testing, information about the new Soviet PT-76 tank became available. The PT-76 was amphibious, and soon there were demands that any U.S. light tank be able to swim as well. The T-92 was already in the prototype stage and could not be easily refitted for this role, so the design of an entirely new system started as the XM551 Sheridan.

The vehicle proved to be very noisy and unreliable under combat conditions. The armor was thin enough that it could be penetrated even by heavy machine gun rounds as well as being highly vulnerable to mines.

Vietnam War

The Sheridan saw extensive action in the Vietnam War, being assigned to nearly all armored cavalry squadrons in country. In 1969, armored cavalry units began replacing their M48 Patton tanks.

The battle reports from the troops were sometimes glowing, while the reports higher up the chain of command were often negative. A 1969 evaluation of the vehicles found the M551 was employed in reconnaissance, night patrol and road clearing, accumulating 39,455 road miles and 520 combat missions, with a ready rate of 81%. Despite vulnerability to rockets and mines, it was judged worth applying modifications and equip all cavalry squadrons with the Sheridan. Washer evaluation 1969.

The Sheridan was much appreciated by the infantry who were desperate for direct-fire support, which generally served in combination with ACAVs (M113s) as armored cavalry units consisted of both M113s and M551s as part of their table of organization and equipment. Armor units consisted solely of tanks (minus headquarters company) and mechanized infantry units consisted solely of M113s. In this role the real problem with the Sheridan was its limited ammunition load of only 20 rounds and 8 missiles (though M551s in Vietnam service were not equipped with missiles or their guidance equipment, increasing the basic load of conventional rounds).

A common field modification was to mount a large steel shield, known as an "ACAV set" (Armored Cavalry Assault Vehicle), around the commander's .50-cal. (12.7 mm) gun, allowing it to be fired with some level of protection. The driver has an unusual rotating hatch which has vision blocks when rotated forward. Included with the set was an extra layer of steel belly armor which was bolted onto the vehicle's bottom, although only covering from the front to halfway to the end, possibly due to weight reasons.

A standard modification made during the mid-1970s was the addition of the "cereal bowl" commander's cupola. This mod came about by the broken rib effect that occurred when the Sheridan fired conventional rounds: the recoil would pitch the tank commander against the armor plating, resulting in cracked ribs.

Post-Vietnam The Army began to phase out the Sheridan in 1978, although at the time there was no real replacement. Nevertheless, the 82nd Airborne were able to keep them on until 1996. The Sheridan was the only air-deployable tank in the inventory, and as an elite force they had considerably more "pull" than general infantry and armor units who were forced to get rid of them. Their units were later upgraded to the M551A1 model, including a thermal sighting system for the commander and gunner.

The Sheridan's only air drop in combat occurred during Operation Just Cause in Panama in 1989, when 14 M551's were deployed; four were transported by C-5 Galaxies and ten were dropped by air, but two Sheridans were destroyed upon landing.Doyle, p. 44, 46 The Sheridans' performance received mixed reviews. They were lauded by their operators and some commanders as providing firepower in needed situations to destroy hard targets. However, the Sheridans' employment of only HEAT rounds limited their effectiveness against reinforced concrete construction.

51 Sheridans were deployed in the Gulf War as some of the first tanks sent. They were not very effective against the Russian-built T-72s. Their role was limited by age and light armor to reconnaissance, possibly 6 or less Shillelagh missiles were firedDoyle, p. 4 at Iraqi bunkers, these fewer than a half-dozen missiles, were the only time that the Shillelagh had been fired in a combat environment, from the inventory of the aforementioned 88,000 missiles produced.

Several attempts to upgun or replace the Sheridan have been made over the years since it was introduced, but none proved successful. Several experimental versions of the Sheridan mounting a new turret carrying the NATO-standard 105 mm gun were made, but the resulting recoil was so great as to make the vehicle almost unusable. Several possible replacements for the M551 were tested as a part of the XM8 Armored Gun System effort of the 1980s, but none of these entered service. The Stryker wheeled M1128 mobile gun system has filled this role in the United States.

Armored Gun System The Armored Gun System was a 1980s program to replace the M551 Sheridan in the 82nd Airborne Division. United Defense's M8 AGS was selected in 1992, but the program was canceled in 1997.

Expeditionary Tank The Expeditionary Tank was developed by Teledyne Vehicle Systems as a competitor to the Armored Gun System program. In the late 1970s Teledyne Vehicle Systems carried out several studies on a highly mobile light tracked vehicle, which could be used for a variety of tasks. The in-house trials lasted from 1980 to 1981. By 1982 a detailed design had been decided. The first prototype was completed in December 1983. A 1986 test firing took place. After the program had proved to be a success, it was discontinued.

Stingray Eliminated from the AGS competition, the Cadillac Gage's Stingray light tank is used by Thailand's armed forces.

M8 armored gun system United Defense' M8 armored gun system was selected in 1992 for further development. Prototypes were made in the 1990s but the program was canceled for budgetary reasons in 1997. The eight-wheeled M1128 mobile gun system replaced this project.

Medium tanks

M46 Patton The mobility of the M26 Pershing was deemed unsatisfactory for a medium tank, as it used the same engine that powered the much lighter M4 Sherman. Work began in 1948 on replacing the power plant in the M26 Pershing. Modifications continued to accumulate, and eventually the Bureau of Ordnance decided that the tank needed its own unique designation. When the rebuild began in November 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 U.S. 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

M47 Patton

Although a new power plant corrected the mobility and reliability problems of the M26 Pershing, the subsequently renamed M46 was considered a stopgap solution that would be replaced later by the T42 medium tank. However, after fighting erupted in Korea, the Army decided it needed the new tank earlier than planned. The M47 Patton was the second tank of the Patton series, and one of the U.S Army's principal medium gun tanks of the Cold War.

It had a 90 mm gun and a crew of 5. The M47 was the U.S. Army and Marine Corps primary tank, intended to replace the M46 Patton and M4 Sherman tanks. Although roughly similar (from a distance) to the later M48 and M60, these were completely new tank designs. Many different M47 Patton models remain in service internationally. The M47 was the last U.S. tank to have a bow-mounted machine gun in the hull. Despite it being the primary tank of the U.S., it never saw combat while in U.S. service.

M48 Patton

In early 1951, the U.S. initiated the design of the M48 Patton, designated the T-48 with a 90 mm cannon.Hunnicutt/p. 85 & 152 The T48 featured a new turret, new redesigned hull and an improved suspension. The hull machine gunner position was removed, reducing the crew to four. Nearly 12,000 M48s were built from 1952 to 1959. The early designs, up to the M48A2, were powered by a gasoline 12-cylinder engine which was coupled with an auxiliary 8-cylinder engine. The gas engines gave the tank a short operating range and were prone to catching fire when hit. This version was considered unreliable.

The M48s saw extensive action during the Vietnam War, with over 600 Pattons deployed.Starry/Hunnicutt The initial M48s landed with the Marines in 1965.Dunstan Remaining Pattons deployed to South Vietnam were in three U.S. Army battalions, the 1-77th Armor near the demilitarized zone, the 1-69th Armor in the Central Highlands, and the 2-34th Armor near the Mekong Delta. Each battalion consisted of approximately 57 tanks. M48s were also used by Armored Cavalry Squadrons until replaced by M551 Sheridan. The M67A1 flamethrower tank (nicknamed the Zippo) was an M48 variant used in Vietnam.