By the 1941 it became clear that Pz.Kpfw. IV"s gun was inefficient against well-armoured tanks. A modification of the tank with more powerful gun was being developed since the beginning of 1941. The requirements for the tank"s gun were changed several times. The final version was a 75-mm gun based on the Pak 40 anti-tank gun. The new modification of the tank was named Pz.Kpfw. IV Ausf.F2. Its mass production began in March of 1942.