Battle of Qarasu

In 1203, the main Ghurid sultan, Ghiyath al-Din Muhammad, passed away. This heavily weakened their ability to project control over Khorasan, and Muhammad recaptured various cities including Merv and Nishapur, and briefly besieged Herat, killing the local governor Alp Ghazi. This prompted Ghiyath's brother Muhammad of Ghor, who oversaw the funeral and became the senior sultan, to attack Ala ad-Din Muhammad's domains and secure control over Khorasan. Attempts at diplomacy failed and Muhammad of Ghor raised a massive force to attack Khwarazm. Ala ad-Din Muhammad moved from Sarakhs to Merv, and divided his forces, breaching the dikes in front of Gurganj ahead and stopping the advance of the Ghurids. The flooding rendered any advance impossible for 40 days until the water cleared up.^[1][2][3][4]

Muhammad of Ghor planned to cross the lush lands surrounding Gurganj once they turned dry with his war elephants (he possessed a force of 140,000 men and 400 elephants, facing Ala ad-Din Muhammad with only 70,000 in a strong defensive position). For multiple days fighting persisted at the Khwarazmian oasis and the Ghurids suffered greatly due to a lack of supplies, but a conclusive engagement took place at the Qarasu Canal running from the Amu Darya east of Gurganj. Both the Ghurids and Khwarazmians suffered heavy losses and the canal's water turned red from the blood,^[3] but Muhammad's troops, who were recruited and experienced from India, managed to force a victory and cause the Khwarazmshah to retreat to Gurganj; desperately outnumbered, he appealed for aid from the Qara Khitai and their Qarakhanid subjects.^[1][2][4]

Both sides suffered substantial casualties, and Muhammad of Ghor was unable to capture Gurganj following the events of the engagement, being forced to retreat south with his exhausted army where he was decisively defeated by Ala ad-Din Muhammad and his Qara Khitai allies at the Battle of Andkhud.^[4][1][5][2]