Genghis Khan, receiving no reparations from the Khwarezem Shah, declares war on Persia, consisting at this time of Khwarezm, Transoxiania, and Khorasan.

The Mongol troops approach the walls of Otrar in autumn 1219.

Shortly before, the Mongols had appeared in Kunya Urgench, the capital of the Khwarezmian Empire, where a war council had taken place and where one of the commanders had proposed to open the battle against the Mongols, but Muhammed II has chosen another way, dispersing his troops by garrisons throughout the towns, allowing the commanders to fight singly.

Despite a heroic defense of the city, its fate is sealed.

The town is destroyed and its population massacred and partially enslaved.

The one hundred thousand- to to one hundred and fifty thousand-man Mongol army, looting and destroying all cities that refuse to surrender, spares only artisans and engineers (whom they recruit, eventually taking them back to their tent-capital at Karakorum to help construct their civilization) as it shatters Otrar and …