Operation Barbarossa was an offensive launched by the Axis Powers in June 22, 1941, being an invasion of the Soviet Union. Over four million Axis troops invaded the Soviet Union. It was part of a long time ambition of Adolf Hitler to conquer the Soviet Union, and was successful. The Red Army was pushed back, and defeated at the Battle of Moscow on July 27, 1941. After that, the Soviet leadership evacuated to the southern city of Ufa. In December 1942, the Battle of Stalingrad ended with an Axis victory. By March 1943, most of the Red Army in Europe had retreated to the Ural Mountains. On March 26, the Siege of Ufa ended with a German victory. Stalin committed suicide minutes before German troops entered his bunker. The Soviet Union was effectively defeated.