itself, the chronicles report that the Polovtsy (Cumans) broke and ran without having fought and that their flight through the Rus’ ranks led to mass confusion and resulted in their slaughter by the Mongols. Rus' defeat The Mongols attacked the coalition army when most of it had crossed the Kalka River. The Mongols appear to have caught the coalition forces by surprise in a fast transition from horse archer fire to massed cavalry charges, because the coalition rout began incredibly quickly: the Rus forces bringing up the rear had not yet arrived on the battlefield by the time the front ranks were dissolving. The armies of Volhynia and Kursk made a gap in their line so that the fleeing Cumans could retreat. However, the Mongol heavy cavalry charged through the newly formed gap and also enveloped them. The army of Chernigov, which was not aware that the battle had started, was advancing when they collided head-on with the retreating Cumans. Using smoke bombs to disrupt the coalition's ability to coordinate, the Mongol cavalry took advantage of the confusion in the Chernigov line and attacked, causing the line to collapse. This, in turn, led to the death of Prince Mstislav of Chernigov. At the same time, the Mongol wings closed around the shattered Rus' army, cutting off its retreat. The surrounded Rus' were hit by volley after volley, accompanied by cavalry charges at any weakness in the formation. As the Mongols were carrying this annihilation out, some of the army – led by Mstislav the Bold – managed to cut their way through the Mongol ring and escape. Mstislav of Kiev arrived to see what remained of the Rus' army fleeing. With his contingent of 10,000 men, he retreated to his stockaded camp, on a hill by the Dnieper. The pursuing Mongol army caught up with Mstislav of Kiev's forces and started to besiege the camp. Intervention of Brodnici Mstislav of Kiev and the Kievan army managed to hold out for three days, but were eventually forced to surrender to Ploscânea. But Ploscânea deceived the Slavs and gave them to Tatars; Ploscânea initially was allied with Slavs and Cumans and was the leader of Brodnici, people from a territory of today Moldova and Romania. Once in control of the camp, the Mongols slaughtered the Kievan army including Mstislav of Kiev and several other noble prisoners. Aftermath The battle was a very