Yugoslavia was invaded and occupied by Nazi Germany and its allies in April 1941. The country collapsed very quickly, in about 11 days, because the army was unprepared and outmatched. After the invasion, Yugoslavia was carved up by Germany, Italy, Hungary, and Bulgaria, and a puppet state called the Independent State of Croatia was created. King Peter II and the royal government fled the country, first going to Greece, then the Middle East, and finally settling in London, where they formed a government-in-exile.
After the occupation, two main resistance movements emerged. One was the Yugoslav Partisans, led by Josip Broz Tito. They were communist, multi-ethnic, and strongly anti-fascist, and their goal was to liberate Yugoslavia and build a socialist federation. The other group was the Chetniks, led by Draža Mihailović. They were Serbian royalists and nationalists who supported the monarchy and claimed to be fighting for the restoration of the old Yugoslav state.
At first, there was limited cooperation between the Partisans and Chetniks in 1941, but this quickly broke down. The split happened because the Chetniks avoided direct confrontation with the Germans, feared a communist revolution more than foreign occupation. Over time, many Chetnik units began collaborating with Italian and German forces to fight the Partisans. They also carried out ethnic massacres against Muslims and Croats.
By 1942 and 1943, the Allies concluded that the Chetniks were no longer a genuine resistance force and shifted their full support to Tito’s Partisans. Tito’s Partisans gradually became a large, disciplined guerrilla army that controlled significant territory. They sabotaged Axis supply lines, liberated towns, and created their own governing institutions in freed areas.
By 1944, they had effectively become a conventional army known as the National Liberation Army of Yugoslavia With help from the Red Army, they liberated Belgrade later that year, and then continued westward, defeating German forces and collaborators.
By May 1945, Yugoslavia was fully liberated, largely by its own forces, which was unusual in occupied Europe. After the war, Tito abolished the monarchy and established socialist Yugoslavia.
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