sentences:  By the 16th century, the Russian ruler had emerged as a powerful, autocratic figure, a Tsar.By assuming that title, the sovereign of Moscow tried to emphasize that he was a major ruler or emperor ("tsar" () represents the Slavic adaptation of the Roman Imperial title/name "Caesar") on a par with the Byzantine emperor or with the Mongol khan.Indeed, after Ivan III married Sophia Palaiologina, the niece of the late Byzantine Emperor Constantine XI Palaiologos, in 1472, the Moscow court adopted Byzantine terms, rituals, titles, and emblems such as the double-headed eagle, which survives in the Coat of Arms of Russia.