Turkish migrations after the sixth century were part of a general
movement of people out of central Asia during the first millennium
A.D. that was influenced by a number of interrelated factors--climatic
changes, the strain of growing populations on a fragile pastoral
economy, and pressure from stronger neighbors also on the move.
Among those who migrated were the Oguz Turks, who had embraced Islam
in the tenth century. They established themselves around Bukhara
in Transoxania under their khan, Seljuk.
Split by dissension among the tribes, one branch
of the Oguz, led by descendants of Seljuk, moved west and entered
service with the Abbasid caliphs of Baghdad.
The Turkish horsemen, known as gazis , were organized into tribal
bands to defend the frontiers of the caliphate, often against their
own kinsmen. However, in 1055 a Seljuk khan, Tugrul Bey, occupied
Baghdad at the head of an army composed of gazis and mamluks (slave-soldiers,
a number of whom became military leaders and rulers). Tugrul forced
the caliph (the spiritual leader of Islam) to recognize him as sultan,
or temporal leader, in Persia and Mesopotamia. While they engaged
in state building, the Seljuks also emerged as the champions of
Sunni (see Glossary) Islam against the religion's Shia (see Glossary)
sect. Tugrul's successor, Mehmet ibn Daud (r. 1063-72)--better known
as Alp Arslan, the "Lion Hero"--prepared for a campaign
against the Shia Fatimid caliphate in Egypt but was forced to divert
his attention to Anatolia by the gazis , on whose endurance and
mobility the Seljuks depended.