Operation Barbarossa, beginning 22 June 1941, was the code name for Germany's invasion of the Soviet Union during World War II. Over the course of the operation, about four million soldiers of the Axis powers invaded the USSR along a 2,900 km (1,800 mi) front, the largest invasion in the history of warfare. In addition to troops, Barbarossa used 600,000 motor vehicles and 750,000 horses. The ambitious operation was driven by Adolf Hitler's persistent desire to conquer the Soviet territories as embodied in Generalplan Ost. It marked the beginning of the pivotal phase in deciding the victors of the war. The German invasion of the Soviet Union caused a high rate of fatalities, estimated at 95% of all German Army casualties that occurred from 1941 to 1944, and 65% of all Allied military casualties from the entire war.