The Balkan Wars were two wars in South-eastern Europe in 1912-1913 in the course of which the Balkan League (Bulgaria, Montenegro, Greece and Serbia) 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 gained in the first conflict.
The background to the wars lies in the incomplete emergence of nation-states on the fringes of the Ottoman Empire during the nineteenth century. Serbians had gained substantial territory during the Russo-Turkish Wars of 1877-78, while Greece acquired Thessaly in 1881 (although it 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 (see map).
Tensions among the Balkan states over their rival aspirations in Macedonia subsided somewhat following intervention by the great Powers in the mid-1800s 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, a group of demonstrating Greek officers (Stratiotikos Syndesmos) urging constitutional revision, removal of the royal family from the leadership of the armed forces 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 Macedonia for expansion. In March 1910, an Albanian insurrection broke out in Kosovo which was covertly supported by the young Turks. In August 1910 Montenegro followed Bulgaria's precedent by becoming a kingdom.
It was during the Balkan Wars when the first ever aerial bombardment was carried out. On October 16, 1912 a Bulgarian military airplane flew on a reconnaissance mission over the Turkish army’s positions in Edirne. During the flight, the pilot and observer dropped bombs placed in specially designed compartments outside the airplane. The bombs were dropped over a Turkish military base.
Initially 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, that resulted in the First Balkan War
Bulgaria sought the lion's share of the liberated Macedonian territories, which resulted in the Second Balkan War.
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 in Sarajevo of the Archduke Francis Ferdinand of Austria in June 1914.
Urlanis estimated in Voini I Narodo-Nacelenie Europi (1960) that in the first and second Balkan war there were 122,000 killed in action, 20,000 dead of wounds, and 82,000 dead of disease.