Mongol invasion of the Khwarazmian Empire

From 1219 to 1221 Genghis Khan led the armies of the Mongol Empire against the Khwarazmian Empire, the dominant Muslim power of Central Asia and eastern Iran. In three years the Mongols destroyed the Shah's realm and laid waste to some of the largest cities of the age, including Bukhara, Samarkand, Gurganj, Merv and Nishapur. The war completed the Mongol conquest of Central Asia and opened the way into Persia.

Both powers had risen quickly. The Khwarazmshahs, based at Urgench (Gurganj) south of the Aral Sea, expanded in the late twelfth century as the Seljuk Empire broke up. Tekish took Khorasan and overthrew the last Seljuk sultan in 1194, and his son Muhammad II, who succeeded in 1200, conquered the Qarakhanid cities of Transoxiana. In the same years Genghis Khan united the Mongol tribes. When his general Jebe destroyed Kuchlug, the usurper who had seized the Qara Khitai, the two empires became neighbours.

Relations began cordially, and Genghis appears to have wanted trade rather than war while he was still fighting the Jin in China. In 1218 he sent a large merchant caravan west. Inalchuq, the Khwarazmian governor of Otrar, seized its goods and killed the merchants as spies. When Genghis demanded his punishment, the Shah refused, executed one envoy and humiliated the others. The Khan left a small force to continue the Chinese war and turned his main army west.

The sizes of both armies are deeply uncertain. Medieval chroniclers gave the Mongols 600,000 or more; modern estimates range from about 75,000 to 200,000, with figures around 120,000 to 130,000 common. Estimates for the Shah run from roughly 40,000 to 200,000. Distrusting his commanders and his powerful mother, Terken Khatun, Muhammad avoided open battle and spread his troops among the garrisons of his cities.

The Mongols besieged Otrar for five months before a traitor opened its gates; Inalchuq was executed. Meanwhile Genghis and his son Tolui crossed the Kyzyl Kum desert and appeared unexpectedly before Bukhara, which surrendered after its garrison failed to break out. The city burned during the looting. Samarkand, reached in March 1220, fell within days, and its defenders were killed despite their surrender. Subutai and Jebe pursued the Shah westwards; Muhammad died on an island in the Caspian Sea in December 1220. Gurganj resisted street by street before falling, after which, according to the chronicles, its people were massacred and the city was flooded.

In 1221 Tolui swept through Khorasan. Merv surrendered on a promise of mercy and its population was then slaughtered; Nishapur, where a son-in-law of Genghis had been killed, was razed. Contemporary writers gave death tolls of hundreds of thousands or more than a million per city, figures modern historians consider exaggerated but which reflect a demographic catastrophe. The Shah's son Jalal al-Din rallied an army and beat a Mongol force at Parwan in September 1221, but Genghis then defeated him on the Indus, and Jalal al-Din escaped to India.

Genghis returned east in 1223 to resume the war against the Jin. Total deaths from the campaign have been estimated at anywhere from two to fifteen million. The conquered lands gave the Mongols a base for later attacks on Georgia and Persia. When the empire divided, the former Khwarazmian lands in Iran passed to the Ilkhanate and the northern cities to the Chagatai Khanate.

Our 1200 map shows Central Asia shortly before the invasion, and the 1279 map shows the region within the Mongol Empire.