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 c. 1299, 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 cause of Ottoman success cannot be attributed to any single factor, and they varied throughout the period as the Ottomans continually adapted to changing circumstances.

The earlier part of this period, the fourteenth century, is particularly difficult for historians to study due to the scarcity of sources. Not a single written document survives from the reign of Osman I, and very little survives from the rest of the century. The Ottomans, furthermore, did not begin to record their own history until the fifteenth century, more than a hundred years after many of the events they describe. It is thus a great challenge for historians to differentiate between fact and myth in analyzing the stories contained in these later chronicles, so much so that one historian has even declared it impossible, describing the earliest period of Ottoman history as a "black hole."

At the beginning of the thirteenth century Anatolia was divided between two relatively powerful states: the Byzantine Empire in the west and the Anatolian Seljuks in the central plateau. Equilibrium between them was disrupted by the Mongol invasion and conquest of the Seljuks following the Battle of Köse Dağ in 1243, and the reconquest of Constantinople by the Byzantine Palaeologos dynasty in 1261, which shifted Byzantine attention away from the Anatolian frontier. Mongol pressure pushed nomadic Turkish tribes to migrate westward, into the now poorly-defended Byzantine territory. From the 1260s onward Anatolia increasingly began to slip from Byzantine control, as Turkish Anatolian beyliks were established both in formerly Byzantine lands and in the territory of the fragmenting Seljuk Sultanate.

...
Wikipedia