The campaign was heralded by the Battle of the Kalka River in 1223, which resulted in a Mongol victory over the forces of several Rus' principalities. The Mongols nevertheless retreated. A full-scale invasion of Rus' by Batu Khan followed, from 1237 to 1240. The invasion was ended by the Mongol succession process upon the death of Ögedei Khan. All Russian states were forced to submit to Mongol rule and became part of the Golden Horde empire, some of which lasted until 1480.
Mongol invaders of Russia enjoyed a level of success never experienced by the Europeans. Why is that?