In the 1960s, West Germany and the United States began a joint project to develop a next-generation main battle tank, codenamed MBT-70. The two countries jointly developed a highly modern main battle tank. The projected new main battle tank would weigh up to 50 tons, necessitating the development of a new tank transporter for this new tank. Therefore, in 1965, another joint West German-American project, the HET-70, began development. After the prototype was completed, cost overruns hit the project in 1970, prompting Germany and the United States to independently pursue development of new main battle tanks and tank transporters. German Fischer led the development of the tractor, while Krupp developed the semi-trailer flatbed. This combination began initial testing in 1971 and was eventually procured in 1976 as the SLT-50-2 "Elephant." Production continued until 1979. A total of 324 tank transporters were produced and delivered to the German army. Six of these were exported to Poland in 2002, along with the Leopard 2A4 main battle tank. It has also been exported to countries like Bahrain and even Saudi Arabia.