In early April 1941, German forces invaded Yugoslavia and within days the country was occupied. Western Slovenia, Montenegro, Kosovo and Dalmatia were occupied and administered by the Italians. Macedonia was annexed by Bulgaria. Eastern Slovenia was annexed by Germany.
Croatia, including all of Bosnia, was made an independent state run by Ustasa, a right-wing paramilitary organization that pursued Nazi and Fascist policies. The Ustasa committed such atrocities against the country’s Serb minority that even the German authorities were alarmed and told the Croatian government to moderate their actions.
In Yugoslavia, two resistance organizations emerged — the royalist Serb Cetniks and the communist Partisans under the leadership of Josip Broz Tito. Tito would ultimately prevail to become the leader of Yugoslavia from the end of World War II until his death in 1980.