The 5 cm PaK 38 (L/60) (5 cm Panzerabwehrkanone 38 (L/60)) was a German anti-tank gun of 50 mm calibre. It was developed in 1938 by Rheinmetall-Borsig AG as a successor to the 3.7 cm Pak 36, and was in turn followed by the 7.5 cm Pak 40. The PaK 38 was first used by the German forces during the Second World War in April 1941. When the Germans faced Soviet tanks in 1941 during Operation Barbarossa, the PaK 38 was one of the few early guns capable of effectively penetrating the 45 mm (1.8 in) armor of the formidable T-34. Additionally, the gun was also equipped with Panzergranate 40 APCR shots which had a hard tungsten core, in an attempt to penetrate the armor of the heavier KV-1 tank. Although it was replaced by more powerful weapons, it remained a potent and useful weapon and remained in service with the Wehrmacht until the end of the war.