The First and Second Balkan Wars occurred from 1912-1913 as Bulgaria, Greece, Montenegro and Serbia formed the Balkan League to drive the Ottoman Empire from Europe. In the First Balkan War, the Balkan League was successful in defeating the Ottomans. However, in 1913 the Second Balkan War broke out as the members of the League fought over the division of the conquered territory, particularly Macedonia. Bulgaria lost this war, weakening Ottoman control but also increasing tensions between the Balkan states that would contribute to conflict leading up to World War I.