Early in 1956, it was decided that the M48 tank should be further developed to produce an improved tank with increased operational range and mobility which would require a minimum of refuelling and servicing as well as incorporating an improved main armament.

In November 1956, a decision was taken to install an AVDS-1790-P compression ignition engine in an M48 tank, which was subsequently tested at Yuma Test Station during the summer of 1957. As a result of a meeting in February 1958, three M48 tanks (designated the M48A2E1) were rebuilt to incorporate the new power pack contemplated for use in the new tank, which had been designated the XM60.

During October and November 1958, several main armament candidates were tested at Aberdeen Proving Ground and, based on the test results, the British 105 mm L7A1 barrel, with the US T254E2 breech, was selected as the main armament for the XM60 and designated the M68 cannon.

In February 1957, the M60 (XM60) vehicle characteristics and production planning schedules were established and, in March 1959, the M60 was classified as Standard A.

The initial bid package for the production of M60 tanks was released in April 1959 and in June of the same year a production contract was awarded to Chrysler Corporation, Delaware Defense Plant, for the production of 180 M60 MBTs. In August 1959, an engineering release bid package was released for the second production buy of M60s to be built at Delaware. Subsequent production buys, beginning with October 1960 production, were made from the Chrysler Corporation Detroit Tank Plant, with production of the M60A3 completed in September 1987.

The M60 entered service with the US Army in 1960 and from October 1962 the tank was succeeded in production by the M60A1 (development designation M60E1). The first M60s had M48-type turrets with 105 mm guns. The M60A1 has the same basic chassis as the M60 but a redesigned turret with greater ballistic protection and other modifications. It carries 63 rounds of 105 mm ammunition rather than 57 as carried by the older M60. For most of the 1960s and early 1970s production of the M60A1 was maintained at a very low rate, the minimum necessary to sustain the production base.

As a result of the Middle East War of 1973 a major effort was made to increase production of the M60A1 for two reasons: to replace M60A1 tanks supplied to Israel and to increase war reserve stocks which were then very low. It took some time to build up production of the M60A1 owing, in the main, to a shortage of hull and turret castings. By 1975, production had been boosted to 48 tanks per month, which increased to 72 a month in 1977 and 104 a month in December 1977. Peak production rate was achieved in October 1978 when 129 vehicles were completed. Production continued at a high rate until April 1979 when it started to drop and by the summer of 1980 it was running at 50 vehicles a month. The last M60A1 was completed in May 1980 and all production after this date was of the M60A3. Production of the M60A3 MBT was expected to be completed in May 1985 after over 15,000 M60 series MBTs had been built but, in May 1985, the DoD notified Congress of a letter of offer for 94 M60A3 MBTs for Egypt at a cost of US$165 million. M60A3s being produced early in 1985 were for Saudi Arabia. Taiwan has also purchased M60A3 hulls from General Dynamics Land Systems. These are used in the M48H MBT programme in Taiwan, additional details of which are given under Taiwan earlier in this section.

The FY80 request was for 116 M60A3s for the US Army and a further 444 for foreign military sales, which were built between April 1981 and July 1982. There was no US Army funding for M60A3 production after FY80 but in FY81, between July and September 1982, 167 M60A3s were built for foreign military sales.

In 1988 it was stated that all M60 series tanks, including those in service with the national guard, will be replaced by 1997.

In early 1991, the US stated that up to 2,000 M60A1/ M60A3 MBTs would be available to other NATO countries, these being Greece, Portugal, Spain and Turkey.

M60 series MBTs took part in Operation Desert Storm in the spring of 1991 when they were used by Egypt (M60A1), Saudi Arabia (M60A3) and the United States Marine Corps (M60A1) with explosive reactive armour packages originally developed for the US Army.

In some of the above countries, deliveries are now under way from the USA. Egypt has, for example, taken delivery of all 700 M60A1 MBTs and, as these become operational, an equivalent number of older T-54/T-55 MBTs must be phased out.

Brazil has recently leased 91 M60A3 MBTs from the USA for a period of five years at a total cost, including training, transport and limited spare parts, of US$15 million.

In mid-1997, the Royal Thai Army requested the purchase of 107 surplus M60A3 TTS MBTs from the USA at a cost of US$100 million.

The hull of the M60A1 is made of cast-steel sections and forged floor plates welded together. It is divided into three compartments: driver's at the front, fighting in the centre and the engine and transmission at the rear.

The driver is seated at the front of the vehicle and is provided with a single-piece hatch cover that opens to the right. Three M27 periscopes are mounted forward of his hatch and an M24 infrared periscope can be installed in a mount in the centre of his hatch cover for driving at night. The M24 has now been replaced by the AN/VVS-2 night viewer, which is of the passive rather than infrared type. A hull escape hatch is provided near the driver's position.

The all-cast-steel turret is in the centre of the vehicle with the loader on the left and the commander and gunner on the right. There is an external stowage basket at the rear of the turret. The loader is provided with a single-piece hatch cover that opens to the rear with an integral M37 periscope which can be traversed through 360°.

The commander has a cupola that can be traversed through 360° by hand, a single-piece hatch cover that opens and swings to the rear, an M28C sight in the forward part and eight vision blocks for all-round observation. The M28C can be replaced by an M36 infrared periscope or an M36E1 passive periscope for night vision. The gunner is seated in front of and below the commander and is provided with an M31 periscope with a magnification of x8 and an M105D telescope with a magnification of x8 and a 7.5° field of view. The M31 periscope can be replaced by an M32 infrared periscope or an M35E1 passive periscope for night engagement of targets. The M17A1 or M17C range-finder has a magnification of x10, a 4° field of view and a range of between 500 and 4,400 m.

The engine compartment at the rear of the hull is separated from the fighting compartment by a fireproof bulkhead, and is equipped with a fire extinguishing system.

The torsion bar suspension system consists of six dual rubber-tyred roadwheels with the idler at the front, drive sprocket at the rear and three track-return rollers. The first, second and sixth roadwheel stations are provided with a hydraulic shock-absorber.

The NBC system of the M60 is of the central air filtration type which pipes fresh air to each crew member via a tube. A full range of night vision equipment is fitted as standard including an infrared searchlight over the 105 mm M68 main armament. The latter is either the AN/VSS-1 or the more recent AN/ VSS-3A. The AN/VSS-3A can be used in both the visible or infrared modes with three types of beam; compact, spread or variable width.

The crew compartment is provided with a heater and a RADIAC NBC detector can be fitted if required. The tank can ford to a depth of 1.219 m without preparation and with preparation to a depth of 2.438 m. It can also be fitted with an M9 bulldozer blade kit on the front of the hull for preparing fire positions and clearing obstacles.

Main armament of the M60, M60A1 and M60A3 tanks is a 105 mm M68 rifled tank gun with a bore evacuator. A well-trained crew can fire between six and eight rds/min. Of the 63 rounds of ammunition carried, 26 are carried in the forward part of the hull, to the left and right of the driver's position, 13 in the turret for ready use, 21 in the turret bustle and the remaining three under the gun.

The 105 mm gun can fire the following types of fixed ammunition:

APDS-T (M728), APFSJ5S-T (M735/M735A1), APFSDS-T (M774), APDS-T (M392A2), APERS-T (M494), HEAT-T (M456 series), TP-T (M467), TP-T (M490), TPDS-T (M724), TPDS (M737), HEP-T (M393A1/M393A2), Dummy (M457), TP-T (M393A1), andSmokeWP-T(M416).

Mounted in the commander's cupola is an M85 12.7 mm (0.50) machine gun with an elevation of +60° and a depression of -15°. Mounted coaxially to the left of the main armament is a 7.62 mm M73 machine gun, replaced by the 7.62 mm M240 weapon.

A number of M60A1s has been updated with the RISE engine, the main armament fully stabilised in both elevation and traverse, the fitting of a top-loading air cleaner, new T142 tracks and improved night vision equipment. Additional details of this programme are given in the entry for the M60A3.

• M60A4

This was never type-classified and was a proposal to further improve the M60A1/M60A3 for the national guard.

• M60A1 with ERA

The US Army was to have fielded an Explosive Reactive Armour (ERA) package for its M60A3 MBTs but, although production did start and quantities were produced, it was decided not to field the system. The US Marine Corps fitted some of its M60A1s with the ERA package, and these were used during Operation Desert Storm early in 1991. By late 1991 however, all M60A1 MBTs had been phased out of service with the US Marine Corps.

In 1993, 10 of these were shipped from the USA to Somalia for use by Italian troops operating as part of United Nations forces.

• M60-2000

This is a private venture development by General Dynamics Land Systems and is essentially an upgraded M60 chassis with a M1A1 turret. Details are given in a separate entry.

• Austrian Army M60A1 MBT Upgrade

Late in 1986, an Austrian joint venture (M60 ARGE) of Steyr-Daimler-Puch and NORICUM, was awarded a contract by the Austrian Army to upgrade 118 M60A1 MBTs to the M60A3 (Passive) configuration, to include a new fire-control system incorporating a laser range-finder system produced by the now Raytheon Systems Company and a Honeywell stabilisation system.

The new AVDS-1790-2C engine was supplied to the Austrian Army to the ARGE and purchased from the US Army's Mainz depot. The engine was upgraded to the AVDS-1790-2CA version.

In addition to upgrading the M60A1 to the M60A3 (Passive), the ARGE performed the complete overhaul of these vehicles. The ARGE purchased the conversion kits and spares for the overhaul from the FMS Corporation (now Marvin Land Systems) of Los Angeles, California, at a total cost of US$36 million.

With all of these modifications the upgraded M60A1 is equivalent to the US M60A3. The first M60A3s were handed over to the Austrian Army in mid-1988 and the last ones in November 1989. The Austrian Army already has 50 new M60A3s.

• Israeli M60 series

Outside the United States, the Israel Defence Force is the largest user of the M60 series. There is a separate entry for the M60 under Israel, as this country has carried out so many improvements to the vehicle.

• Saudi Arabian M60A1s

In early 1988, General Dynamics Services Company was awarded a contract by Saudi Arabia for the upgrading of 150 M60A1 MBTs to the M60A3 standard, with the work carried out in existing Saudi Arabian facilities over a three year period. The first vehicle was handed over in December 1989 and final deliveries were made in May 1991. Modifications to the M60A1 included thermal sights, a new fire-control system, a ballistic computer, a laser range-finder and a thermal sleeve for the 105 mm M68 tank gun.

• Mine roller system

General Dynamics Land Systems has developed a mine roller system that can be fitted to the M60A1 and M60A3 MBTs.

• M9 bulldozer kit

This was developed as a depot retrofit package and is used to give already fielded M60s bulldozing capabilities similar to those of the M728 Combat Engineer Tractor. Full details of this bulldozer are given in Jane's Military Vehicles and Logistics 1999-2000, page 250.

• M60 AVLB

The M60 Armoured Vehicle-Launched Bridge (AVLB) is an M60 fitted with a hydraulic launching mechanism and an aluminium scissors bridge which is launched over the front of the vehicle and weighs 14,470 kg. The bridge takes two minutes to lay and when open has an overall length of 19.202 m and can span a gap of up to 18.288 m. Anniston Army Depot started a programme in 1985 to convert M60A2 tanks into M60A1 AVLBs. The M60 AVLB weighs 55,746 kg with the bridge and 41,685 kg without it. Details of the M48/M60 AVLB are given in Jane's Military Vehicles and Logistics 1999-2000, page 137. In addition to being used by the US Army, M60 AVLBs are used by Israel, Singapore (8) and Spain. In US Army service the M48/M60 AVLB will be replaced by the Heavy Assault Bridge (HAB) based on the M1 MBT chassis.

• Upgraded M60 (AVLB-70)

Late in 1994, it was disclosed that an international industrial team had developed to the prototype stage a new mobility upgrade for not only the M48/M60 AVLB but also forthe M60 series of MBTs which are still being used by many countries.

A contractor team was assembled to fund the development of an AVLB-70 prototype system with team members including Teledyne Vehicle Systems (now General Dynamics Land Systems), Allison Transmission and the Israeli company NIMDA, which have extensive experience in the upgrading of tracked armoured vehicles.

The prototype AVLB-70 was completed at the Anniston Army Depot early in 1994 and has since undergone extensive trials.

Teledyne Vehicle Systems provided the AVLB-70 package with the up-powered version of the AVDS-1790 diesel engine that had already been developed for the Israeli Merkava Mk 3 MBT (the new 1,200 hp AVDS-1790-9A replaced the 900 hp AVDS-1790-6A used in the Merkava Mk 1).

A dieselised version of the Allison Transmission X-1100-3B transmission used in the M1 MBT, designated the X-1100-5, was coupled to the new AVDS-1790 engine to form a new power pack.

The original torsion bar suspension system has been replaced by a General Dynamics Land Systems, hydropneumatic system which has been sold to a number of customers.

NIMDA provided the upgrade package with the integrated hardware in the vehicles driver's compartment.

The prototype AVLB-70 was completed in early 1994 and has already demonstrated a top speed of 64 km/h with an acceleration of 0 to 32 km/h in under eight seconds.

• M728 Combat Engineer Vehicle

The Combat Engineer Vehicle was developed under the designation T118E1 and was standardised in 1963 as the M728. It entered production in 1965 and entered service with the US Army in 1968. By 1983, over 300 vehicles had been completed, with no subsequent production. The M728 is also used by Saudi Arabia and Singapore (12).

The M728 is armed with a short-barrelled 165 mm M135 demolition gun which fires the M123A1 HEP (or HESH) round. A 7.62 mm machine gun is mounted coaxially with the main armament and a 12.7 mm machine gun is mounted in the commander's cupola for ground and anti-aircraft use.

Mounted at the front of the hull is a hydraulically operated dozer blade which is used for clearing obstacles and preparing fire positions. Pivoted towards the front of the turret is an A-frame which can be folded back over the rear of the turret when not required. The two-speed winch at the rear of the turret has a maximum capacity of 11,340 kg. An infrared searchlight similar to that fitted to the M60A1 is mounted over the main armament. The M728 weighs 52,163 kg loaded and has a crew of four: commander, gunner, loader and driver. Full details of the M728 Combat Engineer Vehicle are given in Jane's Military Vehicles and Logistics 1999-2000 page 24. In US Army service the M728 will be replaced by the United Defense Grizzly (Breacher) armoured vehicle based on a modified M1 chassis.

Production complete. In service with the following countries in the accompanying table.