The Mongol invasion of Rus was resumed on 21 December 1237 marking the resumption of the Mongol invasion of Europe, during which the Mongols attacked the medieval powers of Poland, Kiev, Hungary, and miscellaneous tribes of less organized peoples. The European invasion, heralded by the Battle of the Kalka River (1223) was fought between the scout forces of just the two Mongolian generals Subutai and Jebe, whose reconnaissance unit met in battle with the combined force of several Rus' princes.

After fifteen years of peace, the Rus' invasion was followed by Batu Khan's full-scale invasion of Rus' and points west during 1237 to 1240, which only ended with a Mongol succession crisis.

The invasion, facilitated by the breakup of Kievan Rus' in the 12th century, had incalculable ramifications for the history of Eastern Europe, including the division of the East Slavic people into three separate nations (modern day Russia, Ukraine, and Belarus). and the rise of the Grand Duchy of Moscow.

As it was undergoing fragmentation, Kievan Rus' faced the unexpected eruption of an irresistible foreign foe coming from the mysterious regions of the Far East. "For our sins", writes the Rus' chronicler of the time, "unknown nations arrived. No one knew their origin or whence they came, or what religion they practiced. That is known only to God, and perhaps to wise men learned in books".^{[citation needed]}