The result of the Balkan Wars was that the Macedonian region and Adrianople Thrace was partitioned between Bulgaria, Greece, Serbia and the Ottoman Empire (the new state of Yugoslavia was created as after 1918 and started its existence as Kingdom of the Serbs, Croats and Slovenians "SHS"), with Bulgaria getting the smallest share. In 1913 the whole Thracian Bulgarian population from the Ottoman part of Eastern Thrace was forcibly expelled to Bulgaria. IMARO, now led by Todor Aleksandrov, maintained its existence in Bulgaria, where it played a role in politics by playing upon Bulgarian irredentism and urging a renewed war to liberate Macedonia. This was one factor in Bulgaria allying itself with Germany and Austria-Hungary in World War I. During the First World War in Macedonia (1915–1918) the organization supported Bulgarian army and joined to Bulgarian war-time authorities when they took control over Vardar Macedonia temporarily until the end of war. In this period the autonomism as political tactics was abandoned from all internal IMARO streams and all of them shared annexationist positions, supporting eventual incorporation of Macedonia in Bulgaria. IMARO organised the Valandovo action of 1915, which was an attack on a large Serbian force. Bulgarian army, supported by the organization's forces, was successful in the first stages of this conflict, managed to drive out the Serbian forces from Vardar Macedonia and came into positions on the line of the pre-war Greek-Serbian border, which was stabilized as a firm front until end of 1918.