Bulgarian Declaration of Independence in the context of "Eastern Rumelia"

The history of Ottoman Bulgaria spans nearly 500 years, beginning in the late 14th century, with the Ottoman conquest of smaller kingdoms from the disintegrating Second Bulgarian Empire. In the late 19th century, Bulgaria was liberated from the Ottoman Empire, and by the early 20th century it was declared independent.

The brutal suppression of the Bulgarian April Uprising of 1876 and the public outcry it caused across Europe led to the Constantinople Conference, where the Great Powers tabled a joint proposal for the creation of two autonomous Bulgarian vilayets, largely corresponding to the ethnic boundaries drawn a decade earlier with the establishment of the Bulgarian Exarchate.

The Bosnian Crisis, also known as the Annexation Crisis (German: Bosnische Annexionskrise, Turkish: Bosna Krizi; Serbo-Croatian: Aneksiona kriza, Анексиона криза) or the First Balkan Crisis, erupted on 5 October 1908 when Austria-Hungary announced the annexation of Bosnia and Herzegovina, territories formerly within the sovereignty of the Ottoman Empire but under Austro-Hungarian administration since 1878.

This unilateral action – timed to coincide with Bulgaria's declaration of independence from the Ottoman Empire on 5 October – sparked protestations from all the Great Powers and Austria-Hungary's Balkan neighbors, Serbia and Montenegro. In April 1909, the Treaty of Berlin was amended to reflect the fait accompli and bring the crisis to an end. Although the crisis ended with what appeared to be a total Austro-Hungarian diplomatic victory, it permanently damaged relations between Austria-Hungary and its neighbors, especially Serbia, Italy and Russia, and in the long term helped lay the grounds for World War I. Austro-Serbian relations – harmed by the annexation's inflaming of Serbian nationalists – continued to be strained to the point of declaring war on each other in 1914.

The foreign relations of the Ottoman Empire were characterized by competition with the Persian Empire to the east, Russia to the north, and Austria to the west. The control over European minorities began to collapse after 1800, with Greece being the first to break free, followed by Serbia. Egypt was lost in 1798–1805. In the early 20th century Austria-Hungary annexed Bosnia and Herzegovina, the Bulgarian Declaration of Independence soon followed. The Ottomans lost nearly all their European territory in the First Balkan War (1912–1913). The Ottoman Empire allied itself with the Central Powers in the World War I, and was defeated. During the war, the British successfully mobilized Arab nationalism, and the Ottoman Empire thereby lost its Arab possessions, and itself soon collapsed in the early 1920s.