Tank development in the United States after World War II was dominated by the expected conflict with the Soviet Union in Europe. Tank designs were evaluated by criteria that led steadily to faster, heavier, more armored, more powerfully and accurately armed tanks while competing lighter designs were ignored. In the early years of the 21st Century the U.S. forces had the finest heavy forces in the world, but rapid deployment light infantry lacked adequate armor support when the infantry can deploy faster than the heavy armor.
This Olive-Drab.com page reviews the sequence of tanks developed after World War II with links to other pages with more photos and information.
M-26 Pershing Heavy Tank, Texas Military Forces Museum, Camp Mabry, TX, 30 January 2006. Photo: Courtesy of Bob Pettit.
The standard tank for the U.S. Army at the end of World War II was the M26 Pershing, developed to replace the M4 Sherman. While the Pershing was ten tons heavier than the Sherman, it used the same 500hp engine, leaving the Pershing significantly underpowered. In the post-war environment, there was no funding for a new tank so the Army undertook a modernization program, including a new engine, for the 2,000 Pershings in inventory. This was the beginning of a long line of development that extended from the Pershing to the M1 Abrams, from World War II to the 21st Century.
The M46 Patton Tank
M-46 Patton tank, Village of Kumko, Korea, September 1950.
To increase the Pershing's power, the Army chose a V-12 gasoline engine developed by Continental Motors Corporation. Initially designated the M-26E2, after testing, the revamped Pershing, with the new V-12 engine, a better transmission, and other changes, was standardized as the M-46 Patton Medium Tank.
For the M46, the M3A1 90mm gun system was improved and was equipped with the M83 telescopic fire control system. Round transmission access covers on the rear panel were a distinguishing feature.
In 1949, the production of 800 M46 tanks was authorized and the Army proposed converting an additional 1,215 M-26 Pershing tanks to the M46 standard in 1950.
The outbreak of the Korean War in June 1950 forced a reexamination of the tank plans. The number of M46 tanks planned could not meet the needs in Korea and the increasing threat from Soviet intentions in Europe. The increased demand for tanks could not be met by M26 to M46 conversions. In fact, only 319 new M46s became available for service.
The M47 Patton Tank
M47 Patton Tank.
The new situation in 1950 led to an Army decision in September 1950 to proceed with a revised tank design, created from the turret of the developmental T42 medium tank mated to the hull and chassis of the M46, modified with increased armor. This design was standardized as the M47 Patton Tank. The first pilot M47 was shipped to Aberdeen Proving Ground (APG) for testing in March 1951 and production began at Detroit Arsenal in June 1951, before pilot testing was completed. Testing of production M47 tanks began in August 1951 and continued for more than a year.
The testing isolated a number of weaknesses in the M47, notably the complex and fragile rangefinder, the turret stabilization system, and the automatic loader. These items were eliminated from the final production version that was issued to field units. A total of 8,576 M47 Patton tanks were produced by American Locomotive Co. and the Detroit Tank Arsenal before M47 production ended in November 1953.
The M47 was an interim design, the last medium tank to retain the WW II style five man crew and hull machine gun. Eventually all but a few hundred of the M47s were exported to NATO countries where they were the backbone of armor for the next 15 years.
The M48 Patton Tank
M-48 Patton tank and crew, Troop B, 1st Bn, 10th Cavalry Regiment, 4th Infantry Division, Central Highlands, Vietnam, June 1969.
The T48 medium tank began development in late 1950, intended from the beginning to replace the interim M47. It was the first new design, not inherited from the Pershing like the M46 and M47. The new design featured:
Improved armor protection by the use of an elliptical hull and one-piece cast dome turret
Fire control system with range finder, ballistic computer, and ballistic drive
90mm main gun with rapid gun tube replacement (15 min)
810hp gasoline engine AV-1790-5B, same as M47
Cross-drive transmission CD-850-4, same as M47
Four man crew
In December 1950, Chrysler Corporation received an order for six pilot models and 542 M48 production tanks, the start of a planned production of 9,000 M48 tanks by mid-1954. Under the urgency of a perceived inferiority of the American tank force compared to the Soviets, production began even while test and evaluation were still underway. The first pilot M48 was delivered at the end of 1951 and the first production vehicle left Chrysler's Newark, DE plant in March 1952. The M-48 Patton Tank was standardized 2 April 1953.
Between March 1952 and December 1954, approximately 7,000 M48s were produced, and an additional 2,500 were completed by the end of 1956. With the rush to production, the early M48s had significant operational problems with engine, transmission, suspension, and tracks. Correction of these problems delayed full fielding for some time and required continuous improvement of the M48, with variant models M48A1 through M48A5. Production of the M48 ended in 1959 but upgrades to models continued into the 1970s. The M48A3 gained a diesel engine and the M48A5 program, in the mid-1970s, upgraded remaining M48 tanks to the standards of the M60A1, including the 105mm main gun.
The M60 Patton Tank
4th Infantry Brigade (Mechanized) and 14th Panzer Brigade "Brigade 76" M60A1 tanks at Weisbaden, Germany, 14 July 1979. Photo courtesy Melvin Gregory.
In the 1950s, emerging post-war technology led the Army to consider heavy tanks equipped with guided missiles and protection from tactical nuclear weapons. While these developments matured, the Army continued to produce the M48A2. In 1958, the civilian management of military procurement urged faster development of a modernized medium to heavy tank and forbid procurement of the M48A2 after FY1959. Guided missile tanks were too far in the future, so Army focus shifted to a design based on the improved M48, another interim vehicle to fill the need, this time until a guided missile tank could be developed. This decision was the beginning of the M-60 Patton Main Battle Tank program.
The new tank, designated the M60 in March 1959, combined the M48A2 chassis, the Continental AVDS-1790 diesel engine, and the 105mm main gun. Like the M48, it had a four man crew: commander, gunner, loader, and driver. Despite severe limitations on the availability of spare parts and 105mm ammunition, M60 tanks began to arrive at U.S. Army units in Europe in December of 1960. A total of 2,205 M60s were built by Chrysler Corporation at the Newark, DE plant and at the Detroit Arsenal.
Although frequently called a Patton tank informally, the correct nomenclature was Tank, Combat, Full-Tracked, 105mm Gun, M60.
Performance improvements for the M60 were developed from experience with the vehicle, including a longer turret to improve frontal protection (also better suited to the 105mm gun), better suspension, redesigned commander's cupola, T-bar steering, electrical ballistic computer, and a coincidence range finder. These modifications were standardized as the M60A1, a variant that went into production from October 1962 to 1980, a total of 7,948 produced.
During the 1960s the newly developed Shillelagh missile system was adapted to the M60 chassis, the same missile system mounted on the M-551 Sheridan Light Tank. A new turret was designed with smaller profile, better ballistic shape, and improved armor protection. This configuration was standardized as the M60A2 and two pilot vehicles were delivered between November 1965 and February 1966. Against expectations that the M60A2 would be a low risk project, testing revealed problems both with the Shillelagh and the turret. The combustible-cased 152mm ammunition for the gun-launcher was troublesome. When the main gun was fired with conventional ammunition, the recoil jarred the turret throwing the fire control system off target. While orders were placed for 540 M60A2s in 1966-1967, resolving all the problems delayed delivery until 1973 and combat units did not receive them until 1974. Ultimately six armored battalions in Europe were equipped with the M60A2, but the M60A2 had low operational readiness due to the complexity of the gun/missile system. The M60A2 was phased out of active service in 1982.
In 1969, an extensive Product Improvement Program was recommended for the M60A1 to improve reliability, mobility, night operability, and fire on the move capability. Most of these recommendations were implemented between 1971 and 1975. In 1978, a ruby laser range finder and solid-state ballistic computer were added, along with a more reliable coaxial machine gun (7.62mm MG M240). With these and other improvements, the tank was standardized as the M60A3 in 1978, with new production and shipments to units in Europe beginning in 1979. Shortly after production started, two other significant changes were made: the passive night sight was replaced with a thermal sight (TTS) and a meteorological sensor was added.
The M60A3 TTS had significant first-hit advantage over Soviet tanks of its time. In tank battles between Israel and Syria in 1983, the Israelis used their M60A3 to defeat Syria, equipped with the Soviet T72.
Most of the M60A1 and M60A2 tanks in U.S. inventory were depot upgraded to the M60A3 configuration, starting in 1979.
The MBT70 Program and the XM803
German MBT70 prototype, armed with the 120mm main gun.
Thanks largely to the support of then SecDef Robert McNamara, agreement was reached in 1963 between the United States and Germany to jointly develop a main battle tank for central Europe defense, incorporating the latest design concepts and planned to be ready for production by 1970. NATO interoperability was a long-sought objective and the tank program, called MBT-70, would be a significant step in that direction.
Right away, there were conflicting requirements for the MBT-70: The Germans wanted a high-velocity gun while the U.S. wanted a missile system. The Germans wanted the driver in the standard hull position while the U.S. wanted the driver in the turret. The conflicts were resolved, but the U.S. and German teams continued to work on alternative ideas like a U.S. gas turbine engine and a German 120mm cannon.
An analysis by Lockheed recommended five candidate vehicles that met the requirements and a full scale mockup was made of each. After further elimination and reconciliation of designs, a final selection was made and the first pilot produced in the U.S. in July 1967, displayed with a German prototype in September 1967. The MBT70 main armament was a long barreled version of the Shillelagh 152mm gun-launcher used with the M60A2 and M551 plus a secondary, retractable 20mm cannon. By including an automatic loader, the crew was reduced to three, all housed in the turret with the driver in his own counter-rotating capsule. The sophisticated fire control system had a laser range finder, a ballistic computer with digital analyzer, powder temperature sensors, gun deflection due to ambient air conditions, and night vision sights. The innovative hydropneumatic suspension system could raise, lower, or tilt the tank in any direction.
The first MBT70 pilot arrived at APG for testing in late 1969, the first of twelve planned, six in each country. Significant development problems quickly surfaced in the MBT70's complex systems. The cost estimates to finalize development and to produce the tank climbed. In 1969, the new SecDef (David Packard) called for a review of the program that concluded that joint development was not warranted. In 1970, negotiations with Germany concluded with cancellation of the joint MBT70 program.
The Army went its own way to salvage the good ideas from the MBT70 for the next generation main battle tank, disregarding the German components but retaining the basic design. In a revived project called the XM803, the 152mm gun-launcher was retained, combined with desirable features like spaced armor, self-sealing fuel tanks, and blow off vents for ammunition storage. The XM803 simplified the MBT70 package, but was still too complex to be developed and produced within budget constraints. That and remaining suspicion of the 152mm gun-launcher from the M60A2 and M551 experience eventually drained support, after only one pilot model was produced. Congress cancelled funding for the XM803 in December 1971, directing the Army to develop a less costly main battle tank.
The M1 Abrams Main Battle Tank
M1A2 SEP Abrams Main Battle Tank.
From the introduction of the M60 MBT in 1959 to the end of the XM803 program in 1971, no new tank design was fielded by the United States. In that period the Soviet Union did move ahead and its newest tanks threatened the superiority of the M60A3. At the same time that the XM803 was terminated, Congress allocated $20 million to procure prototypes of two new MBT designs for test and evaluation. In January 1972, the Main Battle Tank Task Force was established to set requirements for the new tank. In March of 1972, the Army Chief of Staff directed that the new MBT be fielded within six years, considerably shorter than the normal ten year development period. The task force reported these characteristics, based on analysis of available technologies and known threats:
46-52 tons, combat loaded
Armor protection against the Soviet 115mm gun, internal compartmentalization, external fuel stowage, interior spall liner
105mm or 120mm main gun, .50 cal MG, coaxial 25mm Bushmaster cannon, turret mounted 40mm grenade launcher
First Round Hit Probability
Stationary vehicle vs stationary target: 92% Moving vehicle vs moving target: 58% (Service test with kinetic energy round at 1500m range)
35% of operation off-road
An overall objective for the new design, denoted the XM1 during development, was for it to be a low cost platform that could accommodate technological improvements as they became available. The Army interest in guided missile armament ended with the specification of a conventional gun.
The emphasis on crew survivability arose from the Israeli experience in the 1973 Yom Kippur War when their tanks faced hollow-charged rocket propelled grenades and anti-tank guided missiles. To meet this threat, the MBT design included lower profile, armored bulkheads between the crew and fuel, ammunition storage behind armored doors, blow-off panels on the turret roof to vent explosions upward, a spall liner, and a Halon fire suppression system.
General Creighton Abrams, Army Chief of Staff, decided to increase the XM1's weight to 58 tons, to include the new Chobham composite armor, a British innovation containing multiple layers of materials to defeat hollow-charged weapons.
The XM1 main gun was the same 105mm gun as the M60A3. Its Fire Control System was adapted from components of the MBT70/XM803 and M60A3 systems, including an analog computer, stabilization, thermal sights, a laser range finder, sensors for environmental inputs, and a muzzle sensor to detect gun tube droop.
The first phase of the XM1 program had competition between two contractors, General Motors and Chrysler. In 1973, they were directed to each deliver a prototype tank, automotive test vehicle, and ballistic hull and turret to APG for testing that was conducted during January to May, 1976. The prototypes were examined and the automotive test vehicles were driven more than 3,000 miles. Both contractor's offerings did well in the tests, but the gas turbine powered Chrysler version had slightly greater acceleration. All testing was completed by July 1976, and the competitors were given until November 1976 to refine their bids. Chrysler was awarded the contract, for engineering development of eleven pilot XM1 tanks in a 36 month period.
The Chrysler XM1 pilot tanks were delivered in 1977, followed by further development of the design from February 1978 through September 1979. Within that period -- from April 1978 to February 1979 -- soldiers from 2d Squadron, 3d ACR operated test XM1s. Their evaluation: poor performance with failed engines from dust-clogged air filters and a tendency to throw the track as dirt built up between the sprocket hub and the sponson. These problems were solved and further tests at Ft. Knox, KY went well. At APG survivability tests, the XM1 test vehicle was fired on with various types of ammunition with little damage.
The XM1 was approved for low rate production in May 1979 with a 110 unit order to Chrysler. The first tank came off the assembly line in 1980. The tanks were subjected to field testing for all types of weather, topographical and radioactive environments. Except for continuing problems with the reliability of the gas turbine engine, the tests went well. The new tank was standardized as the M-1 Abrams Main Battle Tank in 1981 with production approved for 7,058 units. The first M1s were provided to combat units in Europe in late 1982 and fielding continued to expand thereafter.
Chrysler Defense, the Chrysler military division, including the M1 MBT program, were acquired by General Dynamics in 1982, renamed General Dynamics Land Systems.
The M1 was planned as a platform that could accept new technology as it became available. The first such upgrade included increased frontal armor, more external stowage, and suspension improvements. These changes were designated as the Improved Performance M1 (M1-IP). In 1985, the first M1A1s were delivered to the Army, featuring a 120mm smooth bore main gun, a microclimate crew cooling system, and NBC overpressure system. By 1989, all units in Europe were equipped with the M1A1. The addition of depleted uranium armor mesh resulted in the M1A1 Heavy Armor variant, with production of 2,329 M1A1 and 2,140 M1A1 (HA) in total by the end of the production run.
In the Gulf War (Operation Desert Shield/Desert Storm, 1990-1991) the M1A1 was used in combat with good results. Desert conditions caused some breakdowns, but operational readiness rates over ninety percent were maintained. The M1A1 thermal sights allowed engagement of targets at night, in sandstorms, and in smoke. First round kills at ranges of 2,000 to 3,000 meters were documented, even through protective berms.
The next set of upgrades, the M1A2, included improvements in the vehicle's electronic systems. The M1A2 Abrams incorporated digital technology to improve navigation, tactical operations, and fire control. Continuous diagnostic technology determines electronic or mechanical failures. The M1A2 retains the 120mm main gun and incorporates a Commanders Independent Thermal Viewer that allows the commander to select one target and the gunner to select a different target, a capability originally developed for the MBT70.
The Army received the first prototype M1A2 in 1990. Initial operational tests showed little improvement over the M1A1 and the program was almost abandoned in the aftermath of the Gulf War. However, sales to foreign governments kept M1A2 production going until 1993. Only a few prototype M1A2s and sixty-two new production units were delivered to the Army with conversion of M1s to M1A2s making up the rest of the fleet. The first M1A2s were provided to 3d Bn, 8th Cavalry in 1995 and to the rest of 1st Cavalry Division receiving M1A2s starting in 1996.
In 1994, another upgrade was ordered, the M1A2 System Enhancement Package (M1A2 SEP). M1A2 SEP includes a second-generation Forward-Looking Infrared Radar (FLIR) gunner's primary sight and commander's independent thermal viewer, Force XXI Battle Command for Brigade and Below (FBCB2), a thermal management system, and improved armor system. The M1A2 SEP entered production in 1999 at a rate of 120 vehicles per year.
In March 2005 the U.S. Army announced the TUSK program for the Abrams, the "Tank Urban Survival Kit." TUSK is a series of enhancements that improve the Abrams’ ability to survive in urban areas off the traditional battlefield for which it was designed. To combat the urban 360° threat, TUSK includes additional protection at the loader’s gun station on the turret, the commander’s gun station, reactive armor to protect the tank’s side from attack by rocket-propelled grenades and slat armor to protect the tank’s rear from the same weapon, and the tank/infantry telephone to allow infantry and armor soldiers to work together in combat.
Material on this page adapted from Transformation: Transition from a Heavy to a Lighter Family of Armored Fighting Vehicles, by Thomas M. Petty, Department of the Army, published by the U.S. Army War College, Carlisle Barracks, PA, 19 March 2001 and augmented by other sources.
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