In the summer of 1963, the defense committee of Bundestag approved the production of a batch of 50 "zero series" Leopards—the first post-war West German tank. However, by that time, work on a new generation machine was already going on, and it was to be put into mass production in the early 1970s. The main requirements were as follows: an ability to fire while on the move off-road, good mobility, best possible protection against radiation, and a strict limit of 32 tons of combat weight. No special attention was paid to the level of projectile protection, as at the time, high mobility and a low silhouette were seen as the basic survival features for a tank. The design, which was developed by Dr. Ing. h.c. F. Porsche AG in cooperation with Wegmann & Co., was submitted for consideration in December 1963, but it was not accepted due to its weight approaching 60 tons.