stylistic:style_transfer, structural:expansion
World War II

At 5:12 a.m. on 6 April 1941, German, Italian and Hungarian forces invaded Yugoslavia. The German Air Force (Luftwaffe) bombed Belgrade and other major Yugoslav cities. On 17 April, representatives of Yugoslavia's various regions signed an armistice with Germany in Belgrade, ending eleven days of resistance against the invading German forces. More than 300,000 Yugoslav officers and soldiers were taken prisoner.

The Axis Powers occupied Yugoslavia and split it up. The Independent State of Croatia was established as a Nazi satellite state, ruled by the fascist militia known as the Ustaše that came into existence in 1929, but was relatively limited in its activities until 1941. German troops occupied Bosnia and Herzegovina as well as part of Serbia and Slovenia, while other parts of the country were occupied by Bulgaria, Hungary, and Italy. From 1941 to 1945, the Croatian Ustaše regime persecuted and murdered around 300,000 Serbs, along with at least 30,000 Jews and Roma; hundreds of thousands of Serbs were also expelled and another 200,000-300,000 were forced to convert to Catholicism.

From the start, the Yugoslav resistance forces consisted of two factions: the communist-led Yugoslav Partisans and the royalist Chetniks, with the former receiving Allied recognition at the Tehran conference (1943). The heavily pro-Serbian Chetniks were led by Draža Mihajlović, while the pan-Yugoslav oriented Partisans were led by Josip Broz Tito.

The Partisans initiated a guerrilla campaign that developed into the largest resistance army in occupied Western and Central Europe. The Chetniks were initially supported by the exiled royal government and the Allies, but they soon focused increasingly on combating the Partisans rather than the occupying Axis forces. By the end of the war, the Chetnik movement transformed into a collaborationist Serb nationalist militia completely dependent on Axis supplies. The Chetniks also persecuted and killed Muslims and Croats, with an estimated 50,000-68,000 victims (of which 41,000 were civilians). The highly mobile Partisans, however, carried on their guerrilla warfare with great success. Most notable of the victories against the occupying forces were the battles of Neretva and Sutjeska.

On 25 November 1942, the Anti-Fascist Council of National Liberation of Yugoslavia was convened in Bihać, modern day Bosnia and Herzegovina. The council reconvened on 29 November 1943, in Jajce, also in Bosnia and Herzegovina, and established the basis for post-war organisation of the country, establishing a federation (this date was celebrated as Republic Day after the war).

The Yugoslav Partisans were able to expel the Axis from Serbia in 1944 and the rest of Yugoslavia in 1945. The Red Army provided limited assistance with the liberation of Belgrade and withdrew after the war was over. In May 1945, the Partisans met with Allied forces outside former Yugoslav borders, after also taking over Trieste and parts of the southern Austrian provinces of Styria and Carinthia. However, the Partisans withdrew from Trieste in June of the same year under heavy pressure from Stalin, who did not want a confrontation with the other Allies.

Western attempts to reunite the Partisans, who denied the supremacy of the old government of the Kingdom of Yugoslavia, and the émigrés loyal to the king led to the Tito-Šubašić Agreement in June 1944; however, Marshal Josip Broz Tito was in control and was determined to lead an independent communist state, starting as a prime minister. He had the support of Moscow and London and led by far the strongest Partisan force with 800,000 men.

The official Yugoslav post-war estimate of victims in Yugoslavia during World War II is 1,704,000. Subsequent data gathering in the 1980s by historians Vladimir Žerjavić and Bogoljub Kočović showed that the actual number of dead was about 1 million.