Answer
The Khwarazmian Empire was invaded by Ögedei Khan during his rule. Ögedei, the third Great Khan of the Mongol Empire, launched a massive campaign against the Khwarazmian Empire in 1219. The invasion was a response to the Khwarazmian ruler Muhammad II's killing of Mongol envoys. Ögedei's forces quickly overwhelmed the Khwarazmian army and conquered much of the empire's territory.