The first Turks to invade Anatolia in force were the Seljuks under Sultan Alp Aslan, who in 1071 defeated a Byzantine army under the emperor Romanus IV at Manzikert, north of Lake Van near what is now the eastern border of Turkey. The Seljuks overran Anatolia and reached the Sea of Marmara before establishing their capital at Nicaea. They were driven out of Nicaea in 1097 by the emperor Alexius I Comnenus and the knights of the First Crusade. The Seljuks then regrouped at Konya (Iconium), which became the capital of the Sultanate of Rum, a realm that comprised most of central and eastern Anatolia.
The Sultanate of Rum reached its peak under sultan Alaeddin Keykubad I (r. 1220–37), who built caravansarais along the highways of central and eastern Anatolia to handle its greatly increased trade, while he and his vezirs adorned Konya and the other cities of the empire with beautiful mosques, medreses (colleges), hospitals, tombs, palaces and bridges, as well as mighty fortresses But the year after Keykubad’s death the Mongols invaded Anatolia, and in 1243 they defeated a Seljuk army at Kösedağ in eastern Anatolia,
breaking the power of the Sultanate of Rum.
The Seljuk sultanate lasted until the beginning of the fourteenth century, though in name only after Kösedağ, when all of central and eastern Anatolia became a Mongol protectorate. But then the Mongols were defeated in 1277 by the Mamluks of Egypt under Sultan Baibars, breaking their power in Anatolia. Baibars himself died later that year, leaving a power vacuum in Anatolia.
