Principality of Chernigov
It was first mentioned in an 1146 chronicle as a part of Principality of Chernigov. Kozelsk became famous in the spring of 1238, when its twelve-year-old prince Vasily, son of Titus, had to defend the town against the army of Batu Khan. The latter dubbed it an "evil town" because its citizens had been fighting the attackers for seven weeks in a row, killing around four thousand enemy soldiers during the siege. The citizens of Kozelsk were greatly outnumbered and almost all of them died in battle.