Warfare with the Seljuk suzerain Atsïz gained his position following his father's death in 1127 or 1128. During the early part of his reign, he focused on securing Khwarazm against nomad attacks. In 1138, he rebelled openly against his suzerain, the
Seljuk Sultan
Ahmad Sanjar and conquered the
Mangyshlak and lower bank of the
Syr Darya, but was defeated in
Hazarasp and forced to flee. Sanjar installed his nephew
Suleiman Shah as ruler of Khwarazm and returned to
Merv. Atsïz returned, however, and Suleiman Shah was unable to hold on to the province. Atsïz then attacked
Bukhara and sacked the city before executing the local client governor. Sanjar was conscious of these developments, but was hoping to prevent furher conflict. Atsiz won more successive victories in a campaign in 1139 against the
Bavandids under
Ali I, an undertaking during which he occupied Gorgan and defeated the provincial
ispahbadh, Ala ad-Dawla 'Ali ibn Shahriyar at the
Battle of Kabud-Jama, capturing him. He was later released upon pleas of his son, in exchange for Gorgan becoming his vassal. By 1141 Atsiz, worried about the expansion of the Qara Khitai, again submitted to Sanjar, who pardoned him and formally returned control of Khwarazm over to him, but this alliance quickly grew tenuous as Ahmad Sanjar started to lack his customary composure and skill. The same year that Sanjar pardoned Atsïz, the
Kara Khitai and
Karluqs under
Yelü Dashi defeated the Seljuks at
Qatwan, near
Samarkand. Atsïz took advantage of the defeat to invade
Khorasan, occupying Merv,
Nishapur, and
Sarakhs. Yelü Dashi, however, sent a force to plunder Khwarazm, forcing Atsïz to pay an annual tribute.
Later Rule In 1142, Atsiz was expelled from Khorasan by Sanjar, who invaded Khwarazm in the following year and forced Atsïz back into vassalage, although Atsïz continued to pay tribute to the Kara Khitai until his death. Sanjar undertook another expedition against Atsïz in 1147 when the latter became rebellious again, besieging Atsiz at Hazarasp and forcing him to seek refuge in
Gurganj, where he again submitted and was pardoned by Sanjar, who was increasingly apprehensive about the burgeoning Qara Khitai to the North-east. In 1152,
Jand was occupied by a band of the Qara Khitai and they assigned
Kamal ad-Din ibn Arslan-Khan Mahmud as the garrison commander. Atsiz marched north and recaptured Jand with little bloodshed in April, imprisong Kamal ad-Din. Atsiz then endowed governorship over Jand to his eldest son,
Il-Arslan, who was given the title of wali. In 1153, Sanjar was defeated and imprisoned by a group of
Oghuz tribes, and Khorasan soon descended into anarchy. The portion of the Seljuk army that refused to join the Oghuz proclaimed the former ruler of the
Karakhanids, Mahmud Khan, as their leader. Mahmud sought an alliance with Atsïz against the Oghuz, while Atsïz's brother Ïnal-Tegin had already plundered a part of Khorasan in 1154. Atsïz and his son
Il-Arslan departed from Khwarazm, but before they could make any gains Sanjar escaped from his captivity and restored his rule. == Death ==