| Mongol conquest of Khorasan | |||||||||
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| Part of the Mongol conquest of the Khwarazmian Empire | |||||||||
.jpg) The ruins of the Tomb of Ahmad Sanjar in Merv, a city which never recovered from the invasion. | |||||||||
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| Belligerents | |||||||||
| Mongol Empire | Khwarezmian Empire | ||||||||
| Casualties and losses | |||||||||
| Light | Devastating | ||||||||
The Mongol conquest of Khorasan took place in 1220-21, during the Mongol conquest of the Khwarazmian Empire. As the Khwarazmian Empire disintegrated after the capture of the large cities of Samarkand and Bukhara by the Mongol Empire, Shah Muhammad II fled westwards in the hope of gathering an army. Genghis Khan ordered two of his foremost generals, Subutai and Jebe, to follow the Shah and prevent any such Khwarazmian resurgence; meanwhile, he sent his youngest son Tolui south to subjugate any resistance.
The region Khorasan contained Silk Road cities such as Merv, Nishapur, and Herat, which were among the largest and richest in the world. Tolui systematically besieged and captured them in turn, pillaging their wealth and executing their inhabitants. Although modern historians regard the figures of medieval chroniclers to be exaggerated (one account has 2.4 million people killed in Nishapur alone), they still estimate the death toll to be in the millions, especially if the resulting famine and starvation is taken into account. The campaign was certainly one of the bloodiest in human history.
Meanwhile, Subutai and Jebe had pursued the Shah to an island on the Caspian Sea, where he died; the two generals, with the Khan's permission, then set out on an expedition around the Caspian Sea, which would take three years. However, the Shah's son, Jalal al-Din, managed to slip through Tolui's forces, and assemble a large army near Ghazni. He inflicted one of the first large Mongol defeats on Shigi Qutuqu at the Battle of Parwan in autumn 1221, but was subsequently defeated by Genghis Khan himself.