The idea of Moscow being the Third Rome was popular since the early Russian Tsars. Within decades after the Fall of Constantinople to Mehmed II of the Ottoman Empire on May 29, 1453, some were nominating Moscow as the "Third Rome", or new "New Rome". Stirrings of this sentiment began during the reign of Ivan III, Grand Duke of Moscow who had married Sophia Paleologue. Sophia was a niece of Constantine XI, the last Eastern Roman Emperor and Ivan could claim to be the heir of the fallen Eastern Roman Empire.
It is noteworthy, that before Ivan III, Stefan Dušan, king of Serbia, and Ivan Alexander, king of Bulgaria, both related to the Byzantine dynasty, facing the decline of the Byzantine empire in the XIV century, made similar claims. Bulgarian manuscripts advanced the idea that Turnovo, the capital of the Bulgarian empire, was the new Constantinople. These plans were never realized as the Ottomans defeated Serbs at Kosovo Polje in 1389, and put an end to the Second Bulgarian Empire in 1396 with the occupation of the Despotate of Vidin. However, the rhethorics developed to this respect earlier in Turnovo was imported to Moscow by Cyprian, a clergyman of Bulgarian origin, who became Metropolitan of Moscow in 1381.
The idea crystallized with a panegyric letter composed by the Russian monk Philoteus (Filofey) in 1510 to their son Grand Duke Vasili III, which proclaimed, "Two Romes have fallen. The third stands. And there will not be a fourth. No one will replace your Christian Tsardom!" Contrary to the common misconception, Filofey explicitly identifies Third Rome with Russia (the country) rather than with Moscow (the city).
Since Roman princesses had married Tsars of Moscow, and, since Russia had become, with the fall of Byzantium, the most powerful Orthodox Christian state, the Tsars were thought of as succeeding the Byzantine Emperor as the rightful ruler of the (Christian) world. The word "tsar," like kaiser, is derived from the word "caesar".
Grand Duke Ivan IV was proclaimed the first Russian Tsar on January 16, 1547. On November 2, 1721, Peter I restyled himself as "Emperor and Autocrat of All Russia". The new title was supposed to reflect both the traditional claims of his predecessors and his success in establishing Imperial Russia as a new European power.
- Dmytryshyn, Basil (transl). 1991. Medieval Russia: A Source Book, 850-1700. 259-261. Harcourt Brace Jovanovich. Fort Worth, Texas.