The 120S MBT was developed by General Dynamics Land Systems as a private venture for the export market and is a follow on to the earlier M60-2000 MBT (Jane's Armour and Artillery 2001-2002).

Development of the 120S commenced in December 2000 and in August 2001 the company rolled out a fully functional prototype of the 120S MBT at their Detroit, Michigan, facility.

This made its first public appearance at the IDEF Exhibition held in Turkey in October 2001, after which it was shown to senior Turkish Land Forces Command (TLFC) officers before returning to the United States. Other countries such as Egypt have also been briefed on the 120S programme.

In the designation 120S the 120 represents the 120 mm smoothbore gun and the S represents speed and survivability. The M60 part of the designation is no longer considered relevant as so much of the tank is new and in appearance it is very similar to the M1A1 Abrams.

General Dynamics Land Systems is the overall design authority of the M60 series MBT and this company has considerable experience in the upgrading of this and other MBTs for the export market as well as the transfer of tank technology abroad.

A good example is the co-production programme with Egypt for the M1A1 MBT where the Egyptian Tank Plant not only assembles the M1A1 but also makes some of the subsystems. This includes the complete hull structure fabrications.

For the 120S programme the M1A1 turret and M60 series chassis was leased from the US Army. To reduce overall life cycle costs, many of the subsystems are already well proven and in many cases in volume production. In the case of the chassis, for example, the transmission, final drive, track and torsion bars are from the M1A1 MBT.

According to the manufacturer, the 120S MBT offers a high performance, low-risk approach to armour upgrade. The system is claimed to combine proven advanced-manufacturing technologies into a complete combat package.

The use of common M60 and M1A1 inventoried hardware results in a fully supportable system with a significant increase in lethality and survivability.

The 120S was initially aimed at the Turkish Land Forces Command (TLFC) M60 upgrade requirement but this competition was subsequently won by Israel Military Industries with their Sabra III upgrade. This contract was awarded without a competition. As of early 2006, there were no sales of the 120S MBT.

The 120S MBT is essentially a combat proven M1A1 turret installed on an upgraded M60 series chassis and a detailed description of each of these is provided in a separate entry. It has been stressed that there is no DU armour in the 120S hull or turret.

While the existing M60 turret could have been upgraded a decision was taken to fit the combat proven M1A1 turret for a number of reasons. This includes the higher level of armour protection and the fact that the 120 mm ammunition is separated in the turret bustle.

The 120S turret is armed with a 120 mm M256 smoothbore gun with a 7.62 mm M240 coaxial machine gun. The commander is provided with a 12.7 mm M2 machine gun while the loader has a 7.62 mm M240 machine gun.

A bank of six electrically operated smoke grenade launchers is mounted either side of the turret firing forwards. In addition, the 120S can also lay its own smoke screen by injecting diesel fuel into the exhaust outlet at the hull rear.

The combat proven 120 mm M256 smoothbore gun can fire a complete range of ammunition from a variety of sources including the US, France, Germany and Israel, all of which has a semi-combustible cartridge case.

The computerised fire-control system enables targets to be engaged while the 120S is moving under day and night conditions with a high first-round-hit probability.

The gunner is provided with day/FLIR stabilised sight with an eye-safe laser range-finder and 240 × 4 or 480 × 2 second-generation thermals although the latter is not cleared for export to all countries at the present time.

The turret is installed on the existing M60 chassis using a simple adapter ring that allows the use of the M1A1 wire race ring with no turret modifications.

The M60 chassis has been fitted with the enhanced torsion bar system of the M1 series MBT to take account of the additional weight of the M1A1 turret as well as the additional armour that would be fitted to production vehicles. The track is the T-158 light weight.

The upgraded suspension coupled with the improved power-to-weight ratio gives a faster speed across country and a more stable firing platform as well as a better ride for the crew.

If required by the customer, the torsion bars could be replaced by hydropneumatic units for improved cross-country ride as well as saving some space inside of the hull.

The upper part of the suspension is fitted with new ballistic skirts and new sponsons are provided for additional storage such as batteries and, if required by the user, additional diesel fuel. These sponsons give a much smoother outline.

The fully functional prototype of the 120S retains the standard M60 series power pack consisting of a General Dynamics Land Systems AVDS-1790 series diesel engine developing 750 bhp.

It is envisioned that production vehicles would have the more powerful General Dynamics Land Systems AVDS-1790-9 diesel developing 1,200 hp. This would be coupled to the Allison X-1100-5 series automatic transmission and M1A1 final drives.

This engine has already been produced in production quantities for the now BAE Systems, Ground Systems Division (previously United Defense) M88A2 armoured recovery vehicle and the Merkava Mk 3 MBT. General Dynamics Land Systems will offer the AVDS series engine with or without the digital electronic fuel-control system.

The existing M60 chassis has been fitted with a mock-up side skirts armour as the armour type and position depends on the user's operational requirement.

General Dynamics Land Systems are offering a number of options for the 120S including alternative power packs (for example MTU diesel coupled to automatic transmission), external auxiliary power unit, appliqué digital command and control computer, thermal driver's viewer, commander's independent thermal view with first- or second-generation FLIR, thermal management system and on board Built In Test Equipment (BITE) to name but a few.