As the empire gradually shrank in size, military power and wealth; especially after the Ottoman economic crisis and default in 1875 which led to uprisings in the Balkan provinces that culminated in the Russo-Turkish War (1877–1878); many Balkan Muslims migrated to the Empire's heartland in Anatolia, along with the Circassians fleeing the Russian conquest of the Caucasus. The decline of the Ottoman Empire led to a rise in nationalist sentiment among its various subject peoples, leading to increased ethnic tensions which occasionally burst into violence, such as the Hamidian massacres of Armenians.