The Khwarazmian Empire was the Central Asian power built by the Turkic Anushtegin dynasty, which rose from provincial governors of Khwarazm — the oasis on the lower Amu Darya, south of the Aral Sea — to rule Persia and much of Central Asia in the 12th and early 13th centuries, before Genghis Khan's Mongol invasion of 1219–1221 destroyed it almost completely.
In 1218 a caravan of merchants reached the border town of Otrar carrying goods and a message of trade from a rising eastern power. The local governor accused them of spying, seized their goods, and had them killed. When envoys arrived to demand redress, the shah executed one and sent the others back shamed. The rising power was Genghis Khan. Within three years his armies had erased one of the largest empires on earth, and the shah who thought he could ignore a distant chief died alone and hunted on an island in the Caspian Sea.