From the late 11th century until the early 13th, Gurganj was the capital of ever expanding Khwarezmian capital, a great metropolis straddling the Amu Darya river. The star of Gurganj, as with the entire Anushtegenid realms, was darkened with the Mongol invasion in 1219. While Mongol forces did not reach Gurganj until 1221, by then most of the empire's territories in Transoxania and Khurasan had already fallen, leaving Gurganj isolated and without hope of reinforcement. The great army sent against Gurganj was commanded by three of the sons of the great conqueror Chinggis Khan: Jochi, Chagatai and Ogedai. Gurganj, despite knowing the price for resistance was destruction, took up arms against the Mongols, despite efforts by Jochi to bring the siege to peaceful conclusion. Jochi had been promised the city as a part of his appanage, and he wanted its valuable position along inner Asian trade routes protected. Jochi's efforts may have hampered the siege, struggling against his brothers in how to conduct it.
A common detail in the sources is that there was an absence of stones around the city to use for catapult projectiles (possibly cleared ahead of time by defenders in preparation?), forcing the Mongols to use sections of mulberry trees hardened by being soaked in water. Considering the Mongols controlled so much of the surrounding territory, we might wonder if this was but a brief solution until supplies were sent from other conquered cities.
While the walls of Gurganj were breached, the Mongols had to take the city street by street over several months, destroying much of it with naptha. When the defenders finally surrendered, they were slaughtered: Mongol casualties had been too high for mercy. Gurganj would be wiped from the map when the nearby dams were destroyed (not necessarily intentionally, as the Mongols would have moved off or killed the local individuals with knowledge to maintain them). While a new settlement would grow nearby (known more commonly as Urgench), only two structures are said to have survived the siege in 1221.
To learn more about the siege of Gurganj, check out my video on it: youtu.be/tproWB3awu8