The First Balkan War, which lasted from October 1912 to May 1913, pitted the Balkan League (Serbia, Greece, Montenegro and Bulgaria) against the Ottoman Empire. The combined armies of the Balkan states overcame the numerically inferior and strategically disadvantaged Ottoman armies and achieved rapid success. As a result of the war, almost all remaining European territories of the Ottoman Empire were captured and partitioned among the allies. Ensuing events also led to the creation of an independent Albanian state. Despite its success, Bulgaria was dissatisfied over the division of the spoils in Macedonia, which provoked the start of the Second Balkan War.

Tensions among the Balkan states over their rival aspirations to the provinces of Ottoman-controlled Rumelia, namely Eastern Rumelia, Thrace and Macedonia, subsided somewhat following intervention by the Great Powers in the mid-19th century, aimed at securing both more complete protection for the provinces' Christian majority and protection of the status quo. By 1867, Serbia and Montenegro had both secured their independence, which was confirmed by the Treaty of Berlin a decade later. But the question of the viability of Ottoman rule was revived after the Young Turk Revolution of July 1908, which compelled the Sultan to restore the suspended Ottoman constitution, and the significant developments in the years 1909–11.

The Balkan Wars were two conflicts that took place in the Balkan Peninsula in south-eastern Europe in 1912 and 1913.

By the early 20th century, Montenegro, Bulgaria, Greece and Serbia had achieved independence from the Ottoman Empire of Turkey. But large parts of their ethnic populations remained under Ottoman rule. In 1912, these countries formed the Balkan League. The First Balkan War broke out when the League attacked Turkey on 8 October 1912 and was ended seven months later by the Treaty of London. After five centuries, Turkey lost virtually all of its possessions in the Balkans.

The Second Balkan War broke out on 16 June 1913. Bulgaria was dissatisfied over the division of the spoils in Macedonia, made in secret by its former allies, Serbia and Greece, and attacked them. The Serbian and Greek armies repulsed the Bulgarian offensive and counter-attacked into Bulgaria, while Romania and Turkey also attacked Bulgaria and gained (or regained) territory. In the resulting Treaty of Bucharest, Bulgaria lost most of the territories it had gained in the First Balkan War.