Despite the end of the Cold War, General Dynamics Land System (GDLS) envisioned a potential customer base of countries equipped with Cold War era tanks like the Patton tanks that want to keep their technological edge by upgrading their existing systems rather than developing or procuring new tanks. GDLS started developing the M60-2000 in late 1999, an upgrade over the M60 platform to keep the tank up-to-date with the new M1 Abrams tank. Aside from updating the components to allow the M60-2000 to maintain similar mobility as the Abrams, the most distinctive feature of the M60-2000 was the use of a M1A1 turret on top of the M60 hull, allowing the tank upgrade to use a 120 mm M256 cannon. During development, the tank name was changed from M60-2000 into 120S. The tank was first marketed as a concept to prospective customers in Europe and the Middle East. The first prototype was produced and revealed in 2001. However, no orders came in for the 120S, and the sole prototype was eventually disassembled in 2003.

The 120S was introduced in Update "Alpha Strike" and while looking like a compressed M1 Abrams, it is a hybrid of capabilities between the M1A1 Abrams and the M60. Firstly, the elephant in the room is the large M1A1 turret planted atop a M60 hull. The turret brings the benefits of being equipped with a 120 mm cannon to defeat most of the 120S' foes as well as the turret armour of the M1A1 Abrams that can resist most incoming shots. However, the hull is where most of the disappointment lies in as it is just a M60 hull, the armour of which is quite negligible against the guns that can be faced and the engine isn't upgraded despite the heavier turret, so mobility is slower than preceding M60s. However, for players that have become accustomed to the M60 playstyle from the previous versions in the US tech tree, the 120S can be a refreshing change of pace with new armor and firepower opportunities.