花剌子模
After a nearly year-long siege of the capital, Yinchuan, although the diverted river accidentally flooded the Mongol camp, the Tangut emperor Li Anquan surrendered in January 1210. For nearly a decade the Western Xia served the Mongols as vassals and aided them in the Mongol–Jin War, but when Genghis invaded the Islamic Khwarazmian dynasty in 1219, Western Xia attempted to break away from the Empire and ally with the Jin and Song dynasties. Angered by this betrayal, in 1225 Genghis Khan sent a second, punitive expedition into Western Xia. Genghis intended to annihilate the entire Western Xia culture, and his campaign systematically destroyed Western Xia cities and the countryside, culminating in the siege of the capital in 1227 along with forays into Jin territory. Near the end of the siege, in August 1227, Genghis Khan died from an uncertain cause, though some accounts say he was killed in action against Western Xia. After his death, Yinchuan fell to the Mongols and most of its population was massacred.