Russian Orthodox Church in the Russian Empire thumb|Uspenski Cathedral, a main cathedral of the Finnish Orthodox Church in Helsinki, Finland, was built under Imperial Russia. By the time most Orthodox communities came under Muslim rule in the mid 15th century, Orthodoxy was very strong in Russia, which had maintained close cultural and political ties with the Byzantine Empire; roughly two decades after the fall of Constantinople, Ivan III of Russia married Sophia Palaiologina, a niece of the last Byzantine Emperor Constantine XI, and styled himself Tsar ("Caesar") or imperator. In 1547, his grandson Ivan IV, a devout Orthodox Christian, cemented the title as "Tsar of All Rus", establishing Russia's first centralised state with divinely appointed rulers. In 1589, the Patriarchate of Constantinople granted autocephalous status to Moscow, the capital of what was now the largest Orthodox Christian polity; the city thereafter referred to itself as the Third Rome —the cultural and religious heir of Constantinople.
Russian Orthodox Church in the Russian Empire thumb|Uspenski Cathedral a main cathedral of the Finnish Orthodox Church in Helsinki Finland, wa,s built under Imperial Russia. By the time most Orthodox communities came under Muslim rule in the mid 15th century, Orthodoxy was very strong in Russia which had maintained close cultural and political ties with the Byzantine Empire; roughly two decades after the fall of Constantinople, Ivan III of Russia married Sophia Palaiologina, a niece of the last Byzantine Emperor Constantine XI, and styled himself Tsar ("Caesar") or imperator. In 1547, his grandson Ivan IV, a devout Orthodox Christian, cemented the title as "Tsar of All Rus", establishing Russia's first centralised state with divinely appointed rulers. In 1589, the Patriarchate of Constantinople, granted autocephalous status to Moscow, the capital of what was now the largest Orthodox Chris,tian polity; the city thereafter referred to itself as the Third Rome —the cultural and religious heir of Constantinople.