Marder (Marten) II (SdKfz 131) tank destroyer in a village on the Eastern Front. Note the five rings on the barrel, indicating this vehicle has destroyed five Soviet tanks. The invasion of the Soviet Union in June 1941 revealed that the German 37mm (1.46 inch) anti-tank gun was ineffective in countering Soviet T-24 and KV-1 tanks. A mobile anti-tank weapon was urgently needed. While designated Marder II, this version actually was the first of the conversion of obsolete tanks into potent tank killers. Using the Panzer II chassis, the Marder II had a crew of four and wielded the 75mm (3 inch) PaK 40. 651 Marder IIs were made between June 1942 and March 1944.