Its original settlement was in the northwest Anatolia (Asian part of the modern Turkey) where it was a small beylik (principality).
However, in 1402, Beyazıt was defeated by Timur, a Turkic conqueror from Turkestan in the Battle of Ankara and the newly annexed beyliks (except Karesi) regained their independence.
During Ottoman expansion, there were only three important Christian territories; Cilician Kingdom of Armenia in Çukurova (Cilicia in south Turkey) was conquered by the Mamluks of Egypt in 1375 and İzmir, a part of Knights Hospitaller, was captured by Timur in 1402.
Towards the end of the 14th century east of Central Anatolia was under the hegemony of a Turkmen leader named Kadı Burhaneddin.
After his death and the short-term Timurid rule of the 15th century, Turkmen tribes in the east were united into a tribal confederation named Akkoyunlu (Turkish for "White Sheep").
His grand vizier Hadim Sinan Pasha defeated Dulkadir Beylik in Southeast Anatolia, a Mamluk vassal in 1516.
Ramazan Beylik, the other Mamluk vassal in Çukurova (Cilicia) voluntarily accepted the Ottoman suzerainty.
[7] After the death of Uzun Hasan of Akkoyunlu, Ismail I of Safavid dynasty gained control of Persia and East Anatolia.
Ottomans annexed most of West Iran and Caucasus by the Treaty of Ferhat Pasha at the end of the renewed war of 1578-1590 during the reign of Murad III.
But after the attack of Shah Abbas of Persia, they had to abandon their 1590-gains by the Treaty of Nasuh Pasha in 1612 during the reign of Ahmed I.
According to Armistice of Mudros Ottoman Empire accepted the loss of all territories in the Arabian Peninsula, Syria, Palestine, Jordan, Lebanon and most of Iraq.
They also offered Aegean coast (as well as Thrace) to Greece and eastern Anatolia to newly established Armenia by the Treaty of Sèvres.
The newly established Turkish Republic kept Mediterranean and Aegean coasts as well as the Eastern Anatolia by the Treaty of Lausanne.