Khwarazmshah Il-Arslan at his coronation, miniature painting from the book Jami' al-Tawarikh (c. 1306–1314), written by Rashid al-Din.
In 1152, Il-Arslan was appointed governor of Jand, an outpost on the Syr Darya that had recently been reconquered by his father. When Atsïz died in 1156, Il-Arslan succeeded him as Shah of Khwarazm. Like his father, he chose to acknowledge the suzerainty of both the Seljuk sultan Sanjar and the Gurkhan of the Kara Khitay.
Sanjar’s death only a few months after Il-Arslan’s accession plunged the Great Seljuk realm of Khorasan into disorder. The ensuing chaos allowed Il-Arslan to cast off Seljuk authority, though he maintained amicable relations with Sanjar’s successor, Mas‘ud. The two were said to have contemplated a joint campaign against the Qara Khitay, though the alliance never came to fruition. Following his father’s example, Il-Arslan sought to extend his influence into Khorasan. In 1160, he actively intervened in the region by providing troops to local allies, yet despite the collapse of Seljuk central power, he achieved no lasting gains against the entrenched regional rulers.
In 1158, Il-Arslan involved himself in the affairs of another Qara Khitay vassal, the Karakhanids of Samarkand. The Karakhanid ruler Chaghrï Khan had persecuted the Qarluqs in his domain, prompting several of their chiefs to flee to Khwarazm and seek Il-Arslan’s aid. Responding to their appeal, he invaded Karakhanid territory, seized Bukhara, and laid siege to Samarkand, where Chaghrï Khan had taken refuge. The latter appealed for assistance to both the Turks of the Syr Darya and the Qara Khitay. The Gurkhan dispatched an army, but its commander hesitated to confront the Khwarazmians. Eventually, peace was brokered on terms compelling Chaghrï Khan to restore the Qarluq leaders to their former positions.
In 1172, the Qara Khitay launched a punitive expedition against Il-Arslan for failing to pay the annual tribute. The Shah mustered his army but soon fell ill, entrusting command to one of his lieutenants. The Khwarazmian forces were defeated, and Il-Arslan died shortly thereafter. His death plunged the realm into brief turmoil, as a dispute over the succession broke out between his sons, Tekish and Sultan Shah
