In July 1943, Hitler launched Operation Zitadelle, the last German offensive on the Eastern Front. It was an attempt to shorten the German lines by eliminating the Kursk salient - created after their defeat at Stalingrad - and was designed to result in the encirclement of the Red Army. In reality the German tanks came up against impenetrable Russian defences: minefields, artillery and anti-tank emplacements, spread through lines 250km deep and manned by Russian troops whose actions often verged on the suicidal. The greatest tank battle in history, Kursk assured the Nazis' defeat and was '