PzKpfw III
With the appearance of the T-34 and KV-1/-2 tanks, rearming the Panzer III with a longer-barrelled and more powerful gun was prioritised. The T-34 was generally invulnerable in frontal combat engagements with the Panzer III until the 50 mm KwK 39 L/60 tank gun was introduced on the Panzer III Ausf. J beginning in the spring of 1942 (this tank gun was based on the infantry's 50 mm Pak 38 L/60 towed anti-tank gun). This could penetrate the T-34's heavy sloped armour frontally at ranges under . Against the KV class of heavy breakthrough tanks, the Panzer III was a significant threat if it was armed with special high-velocity tungsten-tipped armour-piercing (AP) rounds. In addition, to counter enemy anti-tank rifles, starting from 1943, the Ausf. L version began the use of spaced armour sideskirts and screens (known as "Schürzen" in German) around the turret and on the vulnerable hull-sides. However, due to the introduction of the upgunned and better armoured Panzer IV, the Panzer III was, after the German defeat at the Battle of Kursk in the summer of 1943, relegated to secondary/minor combat roles, such as tank-training, and it was finally replaced as the main German medium tank by the Panzer IV and the Panzer V Panther.