In 1861 he freed the Russian serfs (peasants, who were almost enslaved to their owners) from their ties to their masters and undertook a rigorous program of military, judicial and urban reforms, never before attempted in Russia. However, during the second half of his reign Alexander II grew wary of the dangers of his system of reforms, having only barely survived a series of attempts on his life, including an explosion in the Winter Palace and the derailment of a train.
Alexander II was finally assassinated in 1881 by a group of revolutionaries, who threw a bomb at his royal carriage.