The heyday of Kievan Rus as a state fell on the reign of Yaroslav the Wise, and under no prince after him, even under Vladimir Monomakh, Russia did not achieve such greatness. To the invasion of Batu - in the middle of the XIII century - due to incessant princely feuds and the struggle for power, Kievan Rus approached, almost completely losing its former power and unity. The book describes one of the most difficult periods in the history of Russia, when the once strong state of Eastern Europe became a vassal of first the Mongol-Tatar conquerors, and then the Grand Duchy of Lithuania.