Sturmartillerie & Panzerjager, 1939-45 - Bryan Perrett

Originally the German assault gun was designed as an infantry support weapon, but the changing conditions of the battlefields of the Second World War forced it to adapt to perform a number of different roles, most importantly as a tank destroyer, although the infantry support role was never wholly discarded. If the much-glamorised Panzer divisions were the sword of the German army then the assault gun and tank destroyer units were its shield. As the Panzers' grip on the battlefield began to fail, though, it was left to the assault gun and tank destroyer crews to take up the burden.