The M1 series of tanks was developed in the 70’s as a replacement for the venerable M60. Previously, in a joint program with then West Germany, the U.S. produced the MBT-70 in the ‘60’s as a replacement. That never worked. The then new 155mm short barreled cannon, which can fire the Shillelagh missile was prone to break down and jamming. The rest of the vehicle didn’t fare better either and both nations eventually backed out. The Germans went on to produce their own very successful Leopard II MBT while the U.S. went on to eventually produce the M1.