was to definitively expel the Ottomans from Europe. The First Balkan War started on 8 October 1912 and lasted six weeks. Serbians reached Skopje on 26 October. Ottoman forces had left the city the day before. During the conflict, Chetniks, a Serb irregular force razed the Albanian quarter of Skopje and killed numerous Albanian inhabitants from the city. The Serbian annexation led to the exodus of 725 Muslim families which left the city on 27 January 1913. The same year, the city population was evaluated at 37,000 by the Serbian authorities. In 1915, during the First World War, Serbian Macedonia was invaded by Bulgaria, which captured Skopje on 22 October 1915. Serbia, allied to the Triple Entente, was helped by France, Britain, Greece, and Italy, which formed the Macedonian front. Following a great Allied offensive in 1918, the Armée française d'Orient reached Skopje 29 September and took the city by surprise. After the end of the World War, Vardar Macedonia became part of the new Kingdom of Serbs, Croats, and Slovenes, which became "Kingdom of Yugoslavia" in 1929. A mostly foreign ethnic Serb ruling class gained control, imposing a large-scale repression. The policies of de-Bulgarization and assimilation were pursued. At that time part of the young locals, repressed by the Serbs, tried to find a separate way of ethnic Macedonian development. In 1931, in a move to formally decentralize the country, Skopje was named the capital of the Vardar Banovina of the Kingdom of Yugoslavia. Until the Second World War, Skopje experienced strong economic growth, and its population increased. The city had 41,066 inhabitants in 1921, 64,807 in 1931, and 80,000 in 1941. Although in an underdeveloped region, it attracted wealthy Serbs who opened businesses and contributed to the modernization of the city. In 1941, Skopje had 45 factories, half of the industry in the whole of Socialist Macedonia. 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