Rise of the Ottoman Empire
The foundation and rise of the Ottoman Empire is a period of history that started with the emergence of the Ottoman principality in , and ended with the conquest of Constantinople on May 29, 1453. This period witnessed the foundation of a political entity ruled by the Ottoman Dynasty in the northwestern Anatolian region of Bithynia, and its transformation from a small principality on the Byzantine frontier into an empire spanning the Balkans and Anatolia. For this reason, this period in the empire's history has been described as the Proto-Imperial Era. Throughout most of this period, the Ottomans were merely one of many competing states in the region, and relied upon the support of local warlords and vassals to maintain control over their realm. By the middle of the fifteenth century the Ottoman sultans were able to accumulate enough personal power and authority to establish a centralized imperial state, a process which was brought to fruition by Sultan Mehmed II (r. 1451-1481). The conquest of Constantinople in 1453 is seen as the symbolic moment when the emerging Ottoman state shifted from a mere principality into an empire, marking a major turning point in its history.
Turkey
From the second half of the 18th century onwards, the Ottoman Empire began to decline. The Tanzimat reforms of the 19th century, which had been instituted by Mahmud II, were aimed to modernise the Ottoman state in line with the progress that had been made in Western Europe. The efforts of Midhat Pasha during the late Tanzimat era led the Ottoman constitutional movement of 1876, which introduced the First Constitutional Era, but these efforts proved to be inadequate in most fields, and failed to stop the dissolution of the empire. 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 into the Russo-Turkish War of 1877–78, 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.