The siege's length is variable, with historians such as Rashid al-Din Hamadani stating that it lasted for seven months, but it is largely agreed that it ended with the defeat and annihilation of the city in April 1221.

[3] Through a combination of efficient planning and excellent manoeuvering, the Khan's army managed to take the border town of Otrar swiftly, followed by the large cities of Bukhara and Samarkand.

[4] The siege, among others, was witnessed by the Persian biographer Shihab al-Din Muhammad al-Nasawi, who recorded an account in Arabic c.

[5] Genghis sent a detachment, led by his sons Jochi and Chagatai, northwest to lay siege to the former capital of Gurganj.

Immensely wealthy, the city lay on marshy grounds on the delta of the Amu Darya, making it difficult to assault.