Zoe, the daughter of Thomas Palaeologus and the sister of Andreas, was married to the far distant Grand Prince of Moscow, Ivan (John) III, and is known in Russian sources as Sophia Palaeologina. A Russian historian, Kluchevsky, said: As heiress to the declining house of Byzantium, the new Tsarina of Russia had transferred the supreme rights of the Byzantine house to Moscow, as to a new Tsargrad, and there shared them with her husband.
Moscow began to be compared with seven-hilled Rome and called the third Rome. The Grand Prince of Moscow became Tsar of all Orthodoxy, and Moscow as the capital of the Russian state became the new city of Constantine (i.e., a new Constantinople-Tsargrad). A Russian scholar of the beginning of the sixteenth century, the monk Philotheus, wrote; Two Romes have fallen, and the third stands, while a fourth is not to be. The pope called the attention of the successor of Ivan III to his right to defend his patrimony of Constantinople. Thus, the fall of Constantinople and the marriage of Ivan III to Sophia Palaeologina brought up the problem of the rights of the rulers of Moscow, those representatives and defenders of eastern Orthodoxy, to the throne of the Byzantine Empire which was seized by the Ottoman Turks in 1453
General situation in the Empire 
Zoe, the daughter of Thomas Palaeologus and the sister of Andreas, was married to the far distant Grand Prince of Moscow, Ivan (John) III, and is known in Russian sources as Sophia Palaeologina. A Russian historian, Kluchevsky, said: As heiress to the declining house of Byzantium, the new Tsarina of Russia had transferred the supreme rights of the Byzantine house to Moscow, as to a new Tsargrad, and there shared them with her husband.
