The establishment of the Independent State of Croatia emerged amidst the chaotic backdrop of World War II as Axis powers sought to expand their influence in Southeast Europe. The Ustaše movement, a nationalist and fascist organization, capitalized on the disarray following the disintegration of the Kingdom of Yugoslavia. On April 10, 1941, following a swift German invasion of Yugoslavia, the Ustaše proclaimed the formation of the Independent State of Croatia (Nezavisna Država Hrvatska, NDH) in a move that would lead to a contentious regime characterized by collaboration with Nazi Germany and Fascist Italy.

Ante Pavelić, the leader of the Ustaše, became head of the new state, which was recognized by both Germany and Italy. Aimed at unifying ethnic Croats and eliminating perceived threats, the NDH instituted policies of ethnic cleansing against Serbs, Jews, and Roma which resulted in severe human rights abuses and atrocities. The Ustaše not only aimed to consolidate power within Croatia but also sought to assert its independence from external control, drafting new laws that favored an ethnically pure Croatian state.

The capital, Zagreb, became the focal point of this new government, while the regime implemented radical changes in societal structures, education, and the economy to align with its fascist ideals. Consequently, the NDH aligned itself closely with Nazi strategic interests in the Balkans, fostering cooperative efforts on military fronts against Partisan resistance groups and the Allied powers. This regime's reign would last until the tide of war shifted in 1944, leaving a legacy of division and suffering in the region.