In 1218 the governor of an eastern province of Khwarizm mistreated several Mongol emissaries. Chinggis retaliated with a force of more than 200,000 troops, and Khwarizm was eradicated by 1220. A detachment of about 25,000 Mongol cavalry, as part of the Khwarizmian campaign, had crossed the Caucasus Mountains, had skirted the Caspian Sea, and had briefly invaded Europe.

After defeating the Georgians and the Cumans of the Caucasus, the small Mongol expedition advanced in 1222 into the steppes of the Kuban. Combining rapid movement with guile, the Mongols again defeated the Cumans, captured Astrakhan, then crossed the Don River into Russia. Penetrating the Crimea, they stormed the Genoese fortress of Sudak on the southeastern coast, then turned north into what later became known as the Ukraine.

The Mongol leaders now thought they had accomplished their mission. Before returning to Mongolia, however, they decided to rest their troops and to gain more information about the lands to the north and the west. They camped near the mouth of the Dnieper River, and their spies soon were scattered throughout eastern and central Europe.

Meanwhile, a mixed Russian-Cuman army of 80,000 under the leadership of Mstislav, prince of Kiev, marched against the Mongol encampment. Jebe and Subetei, another great Mongol general, sought peace; however, when their envoys were murdered, they attacked and routed Mstislav's force on the banks of the Halha River. Historian Charles Halperin estimated that by this time the "destructive power of the Mongol war machine eclipsed anything the Russians had seen before," and the Kievan Russians found themeselves faced no longer with a renewal of the sporadic raids of the past but with the threat of subjugation and foreign domination. In compliance with a courier message from Chinggis, the expedition then marched eastward. As the Mongols were marching north of the Caspian Sea, Jebe died of illness. In 1224 Subetei led the expedition back, after a trek of more than 6,400 kilometers, to a rendezvous with the main Mongol armies, that were returning from their victories over the Khwarizm.

Data as of June 1989