Isma'il Khandan was the ruler of Khwarazm, an ancient state along the previous Aral Sea

Aral Sea

The Aral Sea was a lake that lay between Kazakhstan in the north and Karakalpakstan, an autonomous region of Uzbekistan, in the south...

, from 1035 to 1041 AD. He was the son of Altun Tash

Altun Tash

Altun Tash was Khwarazm-Shah from 1017 until his death.Altun Tash was originally a slave commander serving the Ghaznavid Sebük Tigin. In 1008 he played a leading role in a battle against the Karakhanids at Sharkhiyan near Balkh, in which the Ghaznavids were victorious...

.

In 1035 Isma'il's brother Harun

Harun, Ghaznavid Governor of Khwarezm

Harun was the de facto ruler of Khwarazm from 1032 to 1035. He was the son of Altun Tash.Following his father's death in 1032, Harun was effectively made governor of Khwarazm by the Ghaznavid sultan Mas'ud...

 was assassinated by his guards at the instigation of the Ghaznavid sultan Mas'ud I of Ghazni

Mas'ud I of Ghazni

Mas'ud I seized the throne of the Ghaznavid Empire upon the death of his father Mahmud from his younger twin Mohammad who had been nominated as the heir upon the death of their father Mahmud of Ghazni. His twin was blinded and imprisoned...

. Isma'il took control of Khwarazm, and like his brother defied Mas'ud and gave support to the Seljuks, who were also hostile to Mas'ud. In response Mas'ud turned to the Oghuz

Oghuz Turks

The Turkomen also known as Oghuz Turks were a historical Turkic tribal confederation in Central Asia during the early medieval Turkic expansion....

 Yabghu (chieftain), Shah Malik

Shah Malik

Shah Malik was the head of the Oghuz Yabghus of Jand and Yengi-kent , and was also Khwarazm Shah ....

, for support, inviting him to take over the governorship of Khwarazm. In the winter of 1040/1041 Isma'il was defeated by Shah Malik and forced to flee to the Seljuks.