Genghis Khan’s invasion

Temujin (about 1155–1227) united the Mongol tribes; at the kurultai on the Onon in 1206 he was proclaimed great khan and received the title “Genghis”. As a result of his conquests the Mongol state bordered the Khwarazmshah’s state directly. The two rulers exchanged envoys to gather information about each other: in 1216 the Khwarazmshah sent an envoy to Genghis Khan, and in 1218 Genghis’s envoys led by Mahmud Yalavach were received by Sultan Muhammad in Bukhara and offered a friendly treaty. That year a large trade caravan (450 merchants and 500 camels according to the sources) was stopped in the border city of Otrar; the governor Ghayirkhan (Inalchuq) seized the goods and killed the merchants. Genghis Khan sent an envoy demanding punishment, but Sultan Muhammad had the envoy killed and sent his two companions back humiliated. Contacts were thus broken and war began. The Khwarazmshah’s army was large, but the state was weakened by governors’ wilfulness and court quarrels, including the faction of his mother Turkan Khatun; some details differ between sources.