1) Germany invaded the Soviet Union in June 1941 with over 3 million troops in Operation Barbarossa, seeking to defeat the Soviets and gain Lebensraum or living space. 2) Despite early successes, German forces were unable to capture Moscow or Leningrad by winter 1941 due to overextended supply lines and stiff Soviet resistance. 3) Major turning points included the battles of Stalingrad from 1942-1943 and Kursk in 1943, where the Soviets halted the German advance and began to push them back westward.