The first mention of the town in the Primary Chronicle dates back to the mid of 1146. People say about Kozelsk: “It is a small town, yet one year older than Moscow”. The town was established on the place of an old settlement of Slavs-Viatichi. In 1238, masses of Mongols and Tatars approached Kozelsk. The population bravely defended their town, Batu Khan left four thousands of his warriors near its walls. Only after seven weeks Tatars managed to break through fortress walls and occupy the town. There were almost no defenders by that time. The outraged Khan ordered to mortify all those, who remained in the town, including children and women, and to rase the town to the ground. Having occupied the town, Tatars were afraid to say its name aloud and called Kozelsk “the evil town”.Since 1445 Kozelsk belonged to Lithuania, and only in 1494 Moscow finally regained the town, having formalised the fact of accession of Kozelsk in the contractual letter between the Great Prince Ivan Vasilievich with Lithuanian Prince Alexander Kazimirovich.
At the beginning of the XVI century, a new fortress was built in Kozelsk to protect borders of Muscovy from the Horde, Lithuanians and Crimean Tatars. Neither fortress walls, nor tree entanglements saved Kozelsk, which stood on the border from enemy attacks, and during its history it was fully destroyed not less than six times. During the reign of Ivan the Terrible, Kozelsk became a place for exile of guilty boyars.
Kozelsk obtained its coat of arms in 1776: “On a dark-red field, marking bloodshed, five silver shields with red crosses are depicted criss-cross testifying of bravery of their defence and unlucky fate, and four golden crosses showing their fidelity”. This coat of arms provided to the town by Catherine the Great reminded of the great deed of inhabitants of the town of Kozelsk in their fight against enemies of their Homeland.
The honorary title “Town of Military Glory” was awarded to Kozelsk by the Decree of the President of the on 5 December 2009 for the courage, resilience and mass heroism demonstrated by defenders of the town in the fight for freedom and independence of their Homeland.
Modern Kozelsk is a green town raising as an amphitheatre on the left bank of Zhizdra. On the right bank of Zhizdra, among the woods, newly restored golden domes of churches and white stone fencing of the architectural monument of the XVIII — XIX centuries Saint Presentation Optina Pustyn friary, famous spiritual centre of the Orthodox Belief of Rus, shine in the sun. In 1989, the monastery was returned to church and restored.