Before Hülegü Khan took western Persia and Baghdad in 1258, he had successfully conquered eastern Persia and crossed the Amu Darya River in January 1256, where he destroyed the fortifications of the militant Islamic sect, the Assassins. After this, his hordes moved westwards and executed the caliph in charge of the western Persian territories: considered to be the centre of the Islamic world. Most of his neighbours were part of the Khan’s empire, including Khwarazm, which was conquered by the first Khan, Genghis Khan, in 1220. Genghis Khan had originally approached Khwarazm with peaceful overtures and even concluded a treaty with them, but when a Mongol caravan and envoys were massacred in Otrar, a two-year war was unleashed, annihilating Khwarazm. The Sultanate of Delhi was also subjected to Mongol raids from 1221–1327, with the Mongols butchering many of the populations flanking its borders.
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