In the 10 years following the Battle of Manzikert in 1071, the Seljuk Turks from Central Asia migrated over large areas of Anatolia, with particular concentrations around the northwestern rim. The Turkish language and the Islamic religion were gradually introduced as a result of the Seljuk conquest, and this period marks the start of Anatolia's slow transition from predominantly Christian and Greek-speaking, to predominantly Muslim and Turkish-speaking (although ethnic groups such as Armenians, Greeks, and Assyrians remained numerous and retained Christianity and their native languages). In the following century, the Byzantines managed to reassert their control in western and northern Anatolia. Control of Anatolia was then split between the Byzantine Empire and the Seljuk Sultanate of Rûm, with the Byzantine holdings gradually being reduced.