In 1223, Mstislav joined a coalition of perhaps 18 princes, which, along with Cuman (Polovtsian) allies, pursued the Mongols from the Dnieper River for nine days and joined battle with them at Kalka River. While three princes were captured and later killed at the battle site, and six more were killed in headlong pursuit back to the Dnieper River, Mstislav is the only prince specifically named among the nine or so who escaped. He managed to escape by cutting loose the boats on the Dnieper River so he could not be pursued.