The 3.7 cm PaK-36, was the standard anti-tank gun of the Wehrmacht in 1940. During the battle of France in 1940 it had trouble dealing with thick armour of French and British tanks. In 1941, when Germany invaded the USSR, the gun was next to useless when confronted with Russian T-34 or KV-series tanks. It was successively replaced by larger calibre weapons, like the 5 cm PaK 38, but there were never enough of them, so it was decided to enhance the capability of the PaK 36 by providing it with new ammunition.