Isidor

Date of birth unknown; died circa 1462. Metropolitan of all Rus’.

Of Greek or Bulgarian origin, Isidor was the abbot of a Byzantine monastery. In 1437, Patriarch Joseph of Constantinople ordained him as head of the Russian church, hoping that Isidor would actively promote the union of the Catholic and Orthodox churches, thus supporting the struggle of Byzantium and Rome against the aggression of the Turks. At the Council of Florence of 1439, Isidor vigorously defended the union but was opposed by Foma, the emissary from Tver’—the sole lay member of the Russian delegation. The Russian princes rejected the union, and Isidor was imprisoned. He fled to Italy in 1441 and became a cardinal of the Catholic Church.