[1] He was the youngest son of Grand Prince Svyatoslav Vsevolodovich of Kiev and Maria Vasilkovna of Polotsk.
[1] However, his father and Rurik Rostislavich failed to reach an agreement on the partition of the lands to be occupied, and thus they returned home.
[2] The first skirmish took place on the banks of the Dnieper River, and in this vanguard battle Mstislav Mstislavich succeeded in defeating a detachment of Mongol troops.
[2] There, without consultation with the princes of Kiev and Chernihiv, Mstislav Mstislavich the Bold and the Cumans attacked the Mongols.
[2] The results were disastrous: their forces were disorganized, and a number of princes, including Mstislav and his son,[1] perished during the flight.