In 1941, during the Second World War, Yugoslavia was invaded by Nazi Germany. Germans seized Skopje 8 April and left it to their Bulgarian allies on 22 April 1941. To ensure bulgarization of the society, authorities closed Serbian schools and churches and opened new schools and a higher education institute, the King Boris University. The 4,000 Jews of Skopje were all deported in 1943 to Treblinka where almost all of them died. Local Partisan detachments started a widespread guerrilla after the proclamation of the "Popular Republic of Macedonia" by the ASNOM on 2 August 1944.