The Russian Empire achieved its greatest size under this monarch
Catherine II
Nicholas I
Nicholas II
Peter I
Paul I
Nicholas I, known as Nicholas the Conqueror. During his rule, 1825 – 1855, the Russian Empire came to encompass over 7.7 million square miles, or 20 million square kilometers. It would have been even larger had other nations of Europe not joined with the Ottoman Empire to stop the spread of Russia in the Crimea.