Serbian and Montenegrin front
The Balkan Wars (Turkish: Balkan Savaşları, literally "the Balkan Wars" or Balkan Faciası, meaning "the Balkan Tragedy") consisted of two conflicts that took place in the Balkan Peninsula in 1912 and 1913. Four Balkan states defeated the Ottoman Empire in the first war; one of the four, Bulgaria, suffered defeat in the second war. The Ottoman Empire lost the bulk of its territory in Europe. Austria-Hungary, although not a combatant, became relatively weaker as a much enlarged Serbia pushed for union of the South Slavic peoples. The war set the stage for the Balkan crisis of 1914 and thus served as a "prelude to the First World War".
By the early 20th century, Bulgaria, Greece, Montenegro and Serbia had achieved independence from the Ottoman Empire, but large elements of their ethnic populations remained under Ottoman rule. In 1912 these countries formed the Balkan League. The First Balkan War had three main causes: