question: Which empire bordered the Mongol Empire to the west in 1218?
sentence: By 1218, as a result of defeat of Qara Khitai, the Mongol Empire and its control extended as far west as Lake Balkhash, which bordered the Khwarezmia (Khwarezmid Empire), a Muslim state that reached the Caspian Sea to the west and Persian Gulf and the Arabian Sea to the south.