The Tank, Combat, Full-Tracked, 152 mm Gun/Launcher XM-803, developed from the MBT-70, was part of the abandoned collaborative U.S. and West German initiative to develop a new main battle tank to replace the existing M60 family of MBT during the 1960s. The program experienced significant challenges from the start, with the United States Army and the German Bundeswehr having diverging doctrines that were not coordinated and were not resolved before the project was too far along to be modified. By the late 1960s, West Germany abandoned the project and the U.S. solely funded the project for the next few years. The MBT-70 was redesigned and designated the XM-803, as an attempt to modify the MBT-70 design into a low-cost substitution using entirely U.S.-made components, resulting in the strikingly similar XM-803 prototype. The biggest cost savings came from switching to less expensive steel armour plates. Costs were also decreased by using an engine built in the U.S. instead of West Germany. The prototype was a little heavier and a little slower compared to the original MBT-70. Despite these savings, the XM-803 design began to match the MBT-70 in sophistication as development progressed and was ultimately terminated. The XM-803 program was cancelled by Congress in December 1971, and work on a new tank program began, the XM-1, which ultimately resulted in the production-model M1 Abrams MBT.
Introduced in Update 1.79 "Project X", the XM-803 offers players unique insights into the pathway of U.S. tank development that ultimately leads to the current-day M1 Abrams MBT. Despite the program's eventual demise, the XM-803 gives several unique capabilities for Cold War U.S. Army ground forces players, particularly the capacity to launch anti-tank guided missiles from the gun barrel, which is unusual in Western MBTs but prevalent in Soviet MBTs. The XM-803 performs very similarly to its ancestor, the MBT-70; however, it suffers from a slightly lower top speed and lacks the original 20 mm cannon mounted on the turret roof. Overall, the MBT strikes a good balance between protection, speed, and firepower, allowing players to easily engage most threats.