World War II
On June 22, the Soviet offensive on the Eastern Front codenamed Operation Bagration, destroyed almost all of the German Army Group Centre. Soon, the Germans were forced to retreat and to defend Ukraine and Poland. The arriving Soviet troops caused uprisings against the German government in Eastern European countries, but they failed to succeed unless they were helped by the Soviets. Another Soviet offensive forced Romania and Bulgaria to join the Allies. Communist Serbian partisans under Josip Broz Tito retook Belgrade with some help from Bulgaria and the Soviet Union. By early 1945, the Soviets had attacked many German-occupied countries: Greece, Albania, Yugoslavia, and Hungary. The Soviets made Finland switch to the Allies.