The development of an advanced tank for Swedish army was performed by Sven Berge. First drafts of the unique vehicle were developed in 1956. By 1961, the design of the new vehicle was finalized, and a wooden prototype was built. Later, the first Strv S1 prototype was built and used for testing of the new type of suspension, which allowed for vertical aiming of the rigidly mounted gun. The Strv S2 prototype was developed by the end of 1962. Both prototypes became the basis for the mass production of the Strv 103 tank.