Siege of Bukhara
The siege of Bukhara took place in February 1220, during the Mongol conquest of the Khwarazmian Empire. Genghis Khan, ruler of the Mongol Empire, had launched a multi-pronged assault on the Khwarazmian Empire ruled by Shah Muhammad II. While the Shah planned to defend his major cities individually, the Mongols laid siege to the border town of Otrar and struck further into Khwarazmia. The city of Bukhara was a major centre of trade and culture in the Khwarazmian Empire, but was located far from the border with the Mongol Empire, and so the Shah allocated fewer than 20,000 soldiers to defend it. A Mongol force, estimated to number between 30,000 and 50,000 men, traversed the Kyzylkum Desert, previously considered impassable for large armies. Bukhara's defenders were caught by surprise and, after a failed sortie, the outer city surrendered within three days on 10 February. Khwarazmian loyalists continued to defend the citadel for less than two weeks, before it was breached and taken. The Mongol army killed everybody in the citadel and enslaved most of the city's population. The Mongols appropriated the work of skilled craftsmen and artisans, conscripting other inhabitants into their armies. Although Bukhara was then destroyed by fire, the destruction was relatively mild compared to elsewhere; within a short space of time the city was once again a centre of trade and learning, and it profited greatly from the Pax Mongolica. Background On the eve of the Mongol invasion, Yaqut al-Hamawi's geographical survey described Bukhara as "among the greatest cities of Central Asia". With a population of close to 300,000 and a library of 45,000 books, the city rivalled Baghdad as a centre of learning and culture. The Po-i-Kalyan mosque, which had been commissioned in 1121, was one of the largest in the world, and contained the Kalyan minaret. The city was guarded by the Ark of Bukhara, a fortress established in the fifth century which served as a citadel; the farmlands were extensively irrigated using water from the River Zeravshan. During the twelfth century, the city had been under the rule of the Qarakhanids, who had historically controlled many of the richest cities in the area, such as Samarkand, Tashkent and Fergana. Nominally vassals of the Qara-Khitai Khanate, the Qarakhanids were allowed to operate autonomously, due to the large population and territory under their control. By 1215, they had been subjugated by the Khwarazmians, also former vassals of the Qara-Khitai, who had expanded from Gurganj into the power vacuum left by the collapsing Seljuk Empire. In 1218, Khwarazmshah Muhammad II was Sultan of Hamadan, Iran and Khorasan, and had established dominion over the Ghurids and the Eldiguzids. The Khwarazmian dynasty had usurped the Qara-Khitai, already destabilized by refugees fleeing the conquests of Genghis Khan, who had begun to establish hegemony over the Mongol tribes. Following the defeat of their common enemy, the Naiman prince Kuchlug, relations between the Mongols and the Khwarazmids were initially strong, but the Shah soon grew apprehensive regarding the Mongols. The chronicler al-Nasawi