Mstyslav Mstyslavych, known as the Successful (Udatnyi), b before 1176, d 1228 in Torcheske, in the Kyiv principality. Senior Rus’ prince; grandson of Rostyslav Mstyslavych. He ruled Trypillia (1193–1203), Torcheske (1203–7, 1227–28), Toropets (1207–8), and the lands of Novgorod the Great (1208–15, 1216–18) and Halych (1219–27). In 1193 and 1203 he waged successful campaigns against the Cumans. In 1212 he and his cousin, Mstyslav Romanovych, drove Vsevolod Sviatoslavych Chermny from Kyiv. From 1219 he battled Hungarian and Polish princes to gain control of the Halych land. In 1221, with the help of the Cuman khan Kotian (his father-in-law) and Mstyslav Romanovych, he defeated a Polish-Hungarian army and finally captured Halych. Both Mstyslavs organized the large military expedition of the southern Rus’ princes against the Tatars that ended in the debacle at the Kalka River and the death of nine princes in June 1223. Later, with the help of his son-in-law Danylo Romanovych of Volhynia (husband of his daughter Anna), Mstyslav fought against Hungarian encroachments in Galicia and with various Galician boyars. Nevertheless he gave Peremyshl to his son-in-law Andrew, the son of Andrew II of Hungary, and bequeathed Halych to him.