The Muscovite ruler emerges gradually as a powerful, autocratic ruler, a tsar.

By assuming that title, the Muscovite prince underscores that he is a major ruler or emperor on a par with the emperor on Constantinople or the Mongol khan.

Indeed, after Ivan III's marriage to Sophia Paleologue, the niece of the last Byzantine emperor, the Muscovite court adopts Byzantine terms, rituals, titles, and emblems such as the double-headed eagle.

At first, the term autocrat connotes only the literal meaning of an independent ruler, but in the reign of Ivan IV (r. 1533-84) it will come to mean unlimited rule.

Ivan IV is crowned tsar and thus is recognized, at least by the Orthodox Church, as emperor.

An Orthodox monk had claimed that, once Constantinople had fallen to the Ottoman Empire in 1453, the Muscovite tsar was the only legitimate Orthodox ruler and that Moscow was the Third Rome because it was the final successor to Rome and Constantinople, the centers of Christianity in earlier periods.

That concept is to resonate in the self-image of Russians in future centuries.