World War II began in Europe with the German invasion of Poland on September 1, 1939. For most of the next two years, German forces conquered or controlled much of continental Europe. At its height, German domination extended from the Atlantic coast of France to the Soviet city of Stalingrad on the Volga River; from the Arctic regions of Norway in the north to the deserts of North Africa. By the end of 1942, however, the Allies were on the offensive and ultimately drove back the German advance. The war in Europe ended with the unconditional surrender of Germany in May 1945.