Which empire did Genghis Khan invade starting in 1219?

Genghis Khan invaded the Khwarezmian Empire beginning in 1219. The campaign targeted a powerful state that controlled much of Central Asia, Iran and surrounding regions, and it ended with the empire’s conquest by Mongol forces in 1221.

The immediate crisis followed a diplomatic and commercial dispute. In 1218, a Mongol trade caravan was seized at Otrar, and its merchants were executed on accusations of espionage. Genghis Khan’s subsequent demand for punishment was rejected, and a Mongol envoy was killed. He treated the incident as a grave insult and assembled a large army for invasion.

The Mongols captured major cities including Bukhara, Samarkand and Merv. The campaign was exceptionally destructive, but it also opened a strategic route into Persia and the wider Islamic world. The Khwarezmian Empire is sometimes confused with the later Ilkhanate: the Ilkhanate was a Mongol successor state established in Iran after the conquest, not the empire Genghis Khan invaded.