After the invasion of the Kingdom of Yugoslavia by the Axis powers on 6 April 1941, the extreme Croat nationalist and fascist Ante Pavelić, who had been in exile in Benito Mussolini's Italy, was appointed "Poglavnik" (leader) of an Ustaše-led Croatian state – the Independent State of Croatia (often called the NDH, from the ). The NDH combined almost all of modern-day Croatia, all of modern-day Bosnia and Herzegovina and parts of modern-day Serbia into an "Italian-German quasi-protectorate". NDH authorities, led by the Ustaše Militia, immediately launched a campaign of mass killings, expulsions and forced religious conversions to Catholicism targeting the Serbian Orthodox population living within the borders of the new state.