It was intended to fight other armoured fighting vehicles and serve alongside the infantry-supporting Panzer IV. However, as the Germans faced the formidable T-34, stronger anti-tank guns were needed. Since the Panzer IV had a bigger turret ring, the role was reversed. The Panzer IV mounted the long barreled 7.5 cm KwK 40 gun and engaged in tank-to-tank battles.

The Panzer III became obsolete in this role and for most purposes was supplanted by the Panzer IV. From 1942, the last version of Panzer III mounted the 7.5 cm KwK 37 L/24, better suited for infantry support. Production of the Panzer III ended in 1943. However, the Panzer III’s capable chassis provided hulls for the Sturmgeschütz III until the end of the war.

One solution was to up-gun the tank with a longer and more powerful 5cm KwK 38 L/42 cannon, and to add more armor to the vehicle. Thus the Panzer III Ausf. J was born. It featured 50mm-thick solid armor plates on the front and rear of the hull, an increase from the previous 30mm-thick armor plates.

Among other modifications, the new armor resulted in a ball-mount MG being fitted on the front superstructure and a redesigned driver’s visor.