[[Слика:Soviet Reichstag.gif|мини|десно|250п|Као знак победе, руски војник подиже совјетску заставу над немачким Рајстагом у Берлину, престоници нацистичке Немачке.]]
Till 1939 the USSR was in strong opposition to nazi Germany, supported republicans of Spain who struggled against German and Italian troops. However in 1938 Germany signed the Munich treaty together with the Western Powers and together with Poland divided Czechoslovakia. The Soviet government being afraid of a German attack to the USSR began diplomatic maneuvers. In 1939 Poland refused to participate in any measures of collective safety and then USSR signed the Molotov-Ribbentrop Pact with Nazi Germany. On September, 17 1939 when German armies were in 150 kilometers from the Soviet border, the Soviet army invaded eastern portions of Poland populated ethnic Ukrainians and Belorussians. USSR fought a war with Finland known as the [[Winter War]] (1939–40). It was won by the Soviet Union, the aggressor, which gained part of the [[Karelian Isthmus]]. Despite Stalin's efforts to stay out of a war against Germany, Germany declared war on the Soviet Union and swept across the border on [[June 22]], []. By November the German army had seized Ukraine, begun its [[siege of Leningrad]], and threatened to capture the capital, Moscow, itself.
However, the Soviet victory at the [[Battle of Stalingrad]] proved decisive, reversing the course of the entire war. After losing this battle the Germans lacked the strength to sustain their offensive operations against the Soviet Union and the Soviet Union held the initiative for the rest of the war. By the end of [], the Red Army had broken through the German siege of Leningrad and recaptured much of Ukraine. By the end of [], the front had moved beyond the [] Soviet frontiers into eastern Europe. With a decisive superiority in troops, Soviet forces drove into eastern Germany, capturing [[Berlin]] in May []. The war with Germany thus ended triumphantly for the Soviet Union.