Ottoman wars in Europe participant Ottoman Empire
Cretan Uprising in 1866.
The decision to increase taxes to Christian nations in the empire's Balkan provinces resulted in widespread outrage that lead to several revolts. The first was the Herzegovinian Uprising in 1875, followed by Bulgarian revolutionaries starting an uprising in April 1876 that was brutaly suppresed (see Batak massacre). Later in June, Serbia and Montenegro jointly declared war on the empire. After six months of inconclusive fighting, international reaction to atrocities committed by Turkish troops forced intervention of the major European powers, which concluded a ceasefire. In December, the Constantinople Conference was organized to deal with the situation and resolve the crisis. However, the Ottoman Empire refused the proposed reforms and withdrew from the Conference. 
Russia, inspired by Pan-Slavism and feeling support in the anti-Ottoman sympathies running throughout Europe, saw the chance to declare war on the Ottoman Empire and fulfill the union of all Orthodox nations in the Balkans under its mantle. That started the eleventh Russo-Turkish War in 1877, fought in the Balkans and in the Caucasus, with Russia leading a coalition with Bulgaria, Romania, Serbia and Montenegro. The coalition won the war, pushing the Ottomans all the way back to the gates of Constantinople. Russians and Ottomans signed the Treaty of San Stefano in early 1878. After deliberations at the Congress of Berlin, which was attended by all the Great Powers of the time, the Treaty of Berlin (1878) provided independence or autonomy for the Christian nations in the empire's Balkan territories, and drastically restructured the map of the region.
Shortly after the war, Austria-Hungary was allowed to militarily occupied Bosnia, which formally continued to be part of the Ottoman territories.
Eastern Rumelia was granted some autonomy in 1878, but then rebelled and joined Bulgaria in 1885. Thessaly was ceded to Greece in 1881, but after Greece attacked the Ottoman Empire to help the Second Cretan Uprising in 1897, Greece was defeated in Thessaly. Crete would gain autonomy in 1898 after the Cretan Revolt (1897–1898).