JR Potts, AUS 173d AB (Updated: 2/22/2015):
In 1963, the US and Germany pioneered a joint venture project to develop a new Main Battle Tank - the German prototype being designated as the "KPz-70" and the US version to be known as "MBT-70" (for the purposes of this article, both will be collectively referred to as the MBT-70). The goal was to build a superior tank system making use of steel-layered tungsten alloy armor and an inner protective shell comprised of spaced layers of extra hard uniform rolled steel armor. Almost from the start the two design teams faced numerous disagreements as to the number of design features to incorporate. The language barrier was one obvious detrimental factor and the rivalry held between the two teams resulted in very little teamwork and major developmental cost overruns. Despite the same need for a combat tank, the requirements of each military differed based on battlefield theories and tactics. Different engines and main guns were selected by both sides and even the use of metric (or "SAE") measurements were argued about so both would, in fact, be used.
Testing began in 1965 and the two teams developed fairly advanced features such as a new crouching hydro-pneumatic suspension system that allowed the tank driver to lower its silhouette to within 4 inches from the ground. This would have helped the system conceal itself amongst tall underbrush while making for a harder target to hit. The suspension could then be raised to allow for better off-road mobility and superb travel on paved roads. The turret would be large enough to house the three-man crew which, in itself, was a vast departure from conventional approaches that always stationed the driver in the lower front hull - apart from the gunnery crew. The American team chose a 152mm gun "launcher" as main armament for their MBT-70 with an XM-150 auto loading cannon rated to fire AP/HE/WP rounds as well as the Shillelagh anti-tank missile - the latter being able to reach out and hit targets out to 3,000 meters. For infantry suppression, there was a 7.62 coaxial machine gun and to protect from low-flying aircraft, a 20mm remote-controlled anti-aircraft cannon would be made available, this installed along the side of the turret and hidden under two hatches. The Germans selected a relatively simpler approach with a 120mm automatic cannon as the primary armament.