theologian and patriarch of Moscow and the Russian Orthodox church who, by his leadership in rallying the church membership in a united effort with the Soviet government to repel the German invasion of 1941, obtained substantial advantages for the church in the postwar period.

The son of an Orthodox priest, Ivan Stragorodsky became a monk after his theological studies, taking the name Sergius, and was nominated successively to several bishoprics, including Finland in 1905 and Nizhny Novgorod, where he became metropolitan, or archbishop, in 1917. Elected a member of the Holy Synod, or Orthodox administrative-theological council, Sergius supported the pro-Soviet schismatic faction of the clergy, called the “Living Church,” in 1922–23, during the political imprisonment of the Moscow patriarch Tikhon, but he publicly repudiated the affiliation after Tikhon's release in June 1923. Sergius went into exile at the patriarch's death in 1925 but returned two years later. After a brief imprisonment he was made patriarchal administrator when he influenced the Orthodox Synod to issue a declaration of solidarity with the Soviet regime, enjoining the faithful to dutifully support the system and directing the clergy to declare their political loyalty or face deposition. Objecting to political pressure, a conservative Orthodox group, the Josephites, led by metropolitan Joseph of Leningrad, refused to recognize Sergius' authority.

During World War II, Sergius directed financial drives to outfit Russian tank units and assisted in setting up field hospitals and refuges for the homeless. With the archbishops of Leningrad and Kiev, he was called to an audience with the Soviet leader Joseph Stalin (Stalin, Joseph) on Sept. 4, 1943, to reach an agreement normalizing church-state relations, the first since the 1917 Bolshevik Revolution. He received permission to open a limited number of religious schools and to convene on September 8 a national synod that elected him patriarch of Moscow and all Russia. The acknowledged status thus given the Russian Orthodox effectively neutralized any claim of legitimacy by the schismatic “Living Church.”