The Sultanate of Rum seceded from the Great Seljuk Empire under Suleiman ibn Qutulmish in 1077, following the Battle of Manzikert, with capitals first at İznik and then at Konya. It reached the height of its power during the late 12th and early 13th century, when it succeeded in taking Byzantine key ports on the Mediterranean and Black Sea coasts. In the east, the sultanate absorbed other Turkish states and reached Lake Van. Trade from Iran and Central Asia across Anatolia was developed by a system of caravanserai. Especially strong trade ties with the Genoese formed during this period. The increased wealth allowed the sultanate to absorb other Turkish states that had been established in eastern Anatolia (Danishmends, Mengujekids, Saltukids, Artuqids).
The Seljuq sultans bore the brunt of the Crusades and eventually succumbed to the Mongol invasion in 1243 (Battle of Köse Dağ). For the remainder of the 13th century, the Seljuqs acted as vassals of the Ilkhanate. Their power disintegrated during the second half of the 13th century. The last of the Seljuq vassal sultans of the Ilkhanate, Mesud II, was murdered in 1308. The dissolution of the Seljuq state left behind many small Anatolian beyliks (Turkish principalities), among them that of the Ottoman dynasty, which eventually conquered the rest and reunited Anatolia to become the Ottoman Empire.
In the 1070s, after the battle of Manzikert, the Seljuk commander Suleiman ibn Qutulmish, a distant cousin of Malik-Shah I and a former contender for the throne of the Seljuk Empire, came to power in western Anatolia. In 1075, he captured the Byzantine cities of Nicaea (İznik) and Nicomedia (İzmit). Two years later, he declared himself sultan of an independent Seljuq state and established his capital at İznik.
Suleyman was killed in Antioch in 1086 by Tutush I, the Seljuk ruler of Syria, and Suleyman's son Kilij Arslan I was imprisoned. When Malik Shah died in 1092, Kilij Arslan was released and immediately established himself in his father's territories.
Kilij Arslan was defeated by soldiers of the First Crusade and driven back into south-central Anatolia, where he set up his state with capital in Konya. In 1107, he ventured east and captured Mosul but died the same year fighting Malik Shah's son, Mehmed Tapar.
Meanwhile, another Rum Seljuq, Malik Shah (not to be confused with the Seljuq sultan of the same name), captured Konya. In 1116 Kilij Arslan's son, Mesud I, took the city with the help of the Danishmends.
Upon Mesud's death in 1156, the sultanate controlled nearly all of central Anatolia. Mesud's son, Kilij Arslan II, captured the remaining territories around Sivas and Malatya from the last of the Danishmends. At the Battle of Myriokephalon in 1176, Kilij Arslan II also defeated a Byzantine army led by Manuel I Komnenos, dealing a major blow to Byzantine power in the region. Despite a temporary occupation of Konya in 1190 by the Holy Roman Empire's forces of the Third Crusade, the sultanate was quick to recover and consolidate its power. During the last years of Kilij Arslan II's reign, the sultanate experienced a civil war with Kaykhusraw I fighting to retain control and losing to his brother Suleiman II in 1196.