In their failed attempt to invade Greece, the Italians were driven out of Santi Quaranta, which Mussolini had renamed Proto Edda after his oldest daughter. Mussolini, embarrassed, had to ask Hitler to help his forces. In a fast moving campaign, the British were driven out of Greece and the Germans occupied Athens on April 27.
As part of that campaign, Yugoslavia was also invaded on April 6. Hitler was angry that Yugoslavian King Peter II had rejected collaboration after Serb army officers began agitating against the Tripartite Pact signed by Yugoslavia on March 25, 1941.
Hitler wanted to punish Yugoslavia. Hitler ordered Belgrade destroyed by air the opening day of the invasion, killing 4,000. Many Serbs hid their arms and waited for a potential uprising, but the Croats did not resist, hoping for the promised independence by Hitler. Serb General Draža Mihailović began resistance operations and King Peter formed a government-in-exile in London.
But the real power in resisting the Germans was in the hands of the Communists under Josef Brozovich, who took the name Tito. He denounced Mihailović as a collaborationist in 1942 and declared a provisional government-in-exile on December 4, 1943. He began to receive aid both from the Soviets and the western Allies, a policy he continued as leader of Yugoslavia after the war. Churchill felt strongly about Yugoslavia and his son, a Commando Major, worked on Tito’s staff. Mihailović and Tito’s forces fought each other as well as the Germans.
Soviet Forces moved on Yugoslavia in 1944. On October 20, 1944, Tito and the Soviets, working together, liberated Belgrade. By the end of 1944 Bulgarian army units were joining with Tito and nearly all of Yugoslavia was free of German control.
Tito had Mihailović executed in July 1946, despite requests of the United States Army Air Force Officers he rescued to testify on his behalf.