In 1217, he defeated the Lithuanians , ruining the vicinity of Polotsk  . It is believed that in 1219, after the death of Rostislav Ryurikovich in Ovruch, his brother Vladimir moved from Smolensk to Ovruch, and Mstislav Davydovich became the Prince of Smolensk. In 1223 the troops of Smolensk participated in the battle of the Kalka River, however, Mstislav Davydovich is not mentioned in the reports on the campaign nor those on the Council of Kiev (1223). The Russian-Polovtsian troops were defeated. In 1225 the northern lands of the Principality of Smolensk were protected by Yaroslav Vsevolodovich Prince of Pereyaslavl with the armies of the Novgorod Republic and the Grand Principality of Vladimir. Mstislav's cousin Davyd Mstislavich of Toropets was killed in the Battle of Usvyaty (1225)).
After the Mstislav;s death, the reign of the Principality of Smolensk was taken for 2 years by his son Rostislav  in violation of the rights of the descendants of Roman Rostislavich and Ryurik Rostislavich. He was thereafter deposed by the eldest of them, Svyatoslav Mstislavich, with the help of the Polotsk troops.
Family and children
Hisife is unknown.
|Rostislav Mstislavich of Smolensk (c1212-c1241)||1212||1241|
|Konstantin Davydovich (1184-c1218)||1184||1210|
|Unknown Davydovna of Smolensk (c1185-c1230)||1185||1230||Gleb Vladimirovich of Ryazan (c1180-1219)|
|Mstislav Davydovich of Smolensk (the younger) (1193-1230)||1193||1230|
|Rostislav Davydovich (c1195-c1240)||1195||1240|