The Mongol invasion of Khwarezmia from 1219 to 1221 marks the beginning of the Mongol conquest of the Islamic states.

The Mongol expansion will ultimately culminate in the conquest of virtually all of Eurasia, save for Western Europe, Fennoscandia, the Byzantine Empire, Arabia, most of the Indian subcontinent, Japan and parts of Southeast Asia.It was not originally the intention of the Mongol Empire to invade the Khwarezmid Empire.

According to the Persian historian Juzjani, Genghis Khan had originally sent the ruler of the Khwarezmid Empire, Ala ad-Din Muhammad, a message seeking trade and greeted him as his neighbor.

The Mongols' original unification of the nomadic tribes in Mongolia, then the Turkmens and other nomadic peoples, had come with relatively little bloodshed, and almost no material loss.

Even his invasions of China, to that point, had involved no more bloodshed than previous nomadic invasions had caused.

Shah Muhammad had reluctantly agreed to this peace treaty, but it was not to last.

The war starts less than a year later, when a Mongol caravan and its envoys are massacred in the Khwarezmian city of Otrar.In the ensuing war, lasting less than two years, the Khwarezmid Empire is destroyed utterly.