During World War II, the Kingdom of Hungary engaged in the military occupation, then annexation, of the Bačka, Baranja, Međimurje and Prekmurje regions of the Kingdom of Yugoslavia. These territories had all been under Hungarian rule prior to 1920, and had been transferred to Yugoslavia as part of the post-World War I Treaty of Trianon. They now form part of several states: Yugoslav Bačka is now part of Vojvodina, an autonomous province of Serbia, Yugoslav Baranja and Međimurje are part of modern-day Croatia, and Yugoslav Prekmurje is part of modern-day Slovenia. The occupation began on 11 April 1941 when 80,000 Hungarian troops crossed the Yugoslav border in support of the German-led Axis invasion of Yugoslavia that had commenced five days earlier. There was some resistance to the Hungarian forces from Serb Chetnik irregulars, but the defences of the Royal Yugoslav Army had collapsed by this time. The Hungarian forces were indirectly aided by the local Volksdeutsche, the German minority, which had formed a militia and disarmed around 90,000 Yugoslav troops. Despite only sporadic resistance, Hungarian troops killed many civilians during these initial operations, including some Volksdeutsche. The government of the newly formed Axis puppet state, the Independent State of Croatia, subsequently consented to the Hungarian annexation of the Međimurje area, which dismayed the Croat population of the region.

Baranya or Baranja is a geographical and historical region between the Danube and the Drava rivers located in the Pannonian Plain. Its territory is divided between Hungary and Croatia. In Hungary, the region is included in Baranya county, while in Croatia, it is part of Osijek-Baranja county.