Ten men reigned as pope during the tumultuous period at the turn of the fifth century. The first, Pope Liberius, began his papacy in 352 CE. Pope Liberius refused to condemn Athanasius of Alexandria, the chief defender of Trinitarianism against Arianism. Instead he wrote to Emperor Constantius II asking for council to be called to denounce Arianism as a heresy. However, Constantius II, sympathized with the Arians, and forced the pope’s messenger to sign a writ of condemnation. Unable to persuade Pope Liberius to condemn Athanasius, the Emperor imprisoned him and appointed Felix II as a “puppet” pope in 355 CE.
After three years in exile Liberius returned to Rome. The emperor proposed that Liberius govern the church jointly with Felix II, but the Roman population refused to recognize Felix II and expelled him from the city. Neither Liberius nor Felix took part in the Council of Rimini in 359 CE, and after the death of the Emperor Constantius II in 361 CE, Liberius annulled the decrees of that assembly.
Living in exile from Rome, Felix remained pope until his death in 365 CE. Some historians claim that Pope Liberius eventually relented in his opposition to Arianism and resigned the papacy validating the reign of Felix II. Most assert on the contrary that Pope Liberius adhered staunchly to the orthodoxy of the Trinitarian belief through the end of his pontificate and death in 366 CE. The Eastern Orthodox Church reveres him as a saint, while the Roman Catholic Church does not.