The Balkan Wars were two wars in South-eastern Europe in 1912-1913 in the course of which the Balkan League (Serbia, Montenegro, Greece and Bulgaria) first conquered Ottoman-held Macedonia and most of Thrace and then fell out over the division of the spoils, Bulgaria suffering defeat at the hands of her former allies and losing much of what she had been promised in the initial partition scheme.
The wars were an important precursor to World War I, to the extent that Austria-Hungary took alarm at the great increase in Serbia's territory and regional status. This concern was shared by Germany, which saw Serbia as a satellite of Russia. Serbia's rise in power thus contributed to the two Central Powers' willingness to risk war following the assassination of the Austrian Archduke Francis Ferdinand in Sarajevo in June 1914.
The background to the wars lies in the incomplete emergence of nation-states on the fringes of the Ottoman Empire during the nineteenth century. Serbia had gained substantial territory during the Russo-Turkish War of 1877-78, while Greece acquired Thessaly in 1881 (although she lost a small area to Turkey in 1897) and Bulgaria (an autonomous principality since 1878) incorporated the formerly distinct province of Eastern Rumelia (1885). All three as well as tiny Montenegro sought additional territories within the large Turkish-ruled regions known as Albania, Macedonia and Thrace.
Tensions among the Balkan states over their rival aspirations in Macedonia subsided somewhat following intervention by the great Powerss in the mid-1900s aimed at securing both fuller protection for the province's Christian majority and protection of the status quo. The question of Ottoman rule's viability revived, however, after the Young Turk revolution of July 1908 compelled the Sultan to restore the suspended Ottoman constitution.
While Austria-Hungary seized the opportunity of the resulting Ottoman political uncertainty to annex the formally Ottoman province of Bosnia-Herzegovina, which it had occupied since 1878, Bulgaria declared itself a fully independent kingdom (October 1908) and the Greeks of Crete proclaimed unification with Greece, though the opposition of the great powers prevented the latter action from taking practical effect.
Frustrated in the north by Austria-Hungary's incorporation of Bosnia with its 825,000 Orthodox Serbs (and many more Serbs and Serb-sympathizers of other faiths), and forced (March 1909) to accept the annexation and restrain anti-Habsburg agitation among Serbian nationalist groups, the Serbian government looked to formerly Serb territories in the south, notably "Old Serbia" (the Sanjak of Novi Pazar and the province of Kosovo).
On August 28, 1909, demonstrating Greek officers urging constitutional revision and a more nationalist foreign policy secured the appointment of a more sympathetic government which they hoped would resolve the Cretan issue in Greece's favour and reverse the defeat of 1897. Bulgaria, which had secured Ottoman recognition of her independence in April 1909 and enjoyed the friendship of Russia, also looked to districts of Ottoman Thrace and north-eastern Macedonia for expansion. In March 1910, an Albanian insurrection broke out in Kosovo. In August 1910 Montenegro followed Bulgaria's precedent by becoming a kingdom.
Intially under the encouragement of Russian agents, a series of agreements were concluded: between Serbia and Bulgaria in March 1912 and between Greece and Bulgaria in May 1912. Montenegro subsequently concluded agreements between Serbia and Bulgaria respectively in October 1912. The Serbian- Bulgarian agreement specifically called for the partition of Macedonia.
Then on October 8, 1912 the First Balkan War began when Montenegro declared war against Turkey - pre-empting a warning from Russia and Austria-Hungary. Albania declared independence on November 28, 1912. On December 2, the Balkan League signed an armistice with Turkey ending the war. Turkey withdrew to the Enos-Media Line. An initial peace was concluded at the Treaty of London in May 1913.
By the time of the Armistice, Serbia, Montenegro and Greece had overrun Albania. At the Treaty of London, Austria-Hungary and Italy strongly supported the creation of an independent Albania. In light of this, Serbia and Greece sought compensation from the Macedonian territories that had been overrun by Bulgaria. Bulgaria unsuccessfully attempted to resist this by force of arms. Defeated by Serbia, Greece, Montenegro, Romania and Turkey, Bulgaria signed an Armistice on July 31, 1913. At the Treaty of Bucharest in August 1913, the final territorial adjustments were made.