The Council of Serdica, or Synod of Serdica (also Sardica located in modern day Sofia, Bulgaria), was a synod convened in 343 at Serdica in the civil diocese of Dacia, by Emperors Constans I, augustus in the West, and Constantius II, augustus in the East. It attempted to resolve the Arian controversy, and was attended by about 170 bishops. It was convened by the two augusti at the request of Pope Julius I. Background The first ecumenical council (Nicaea I) canon 5 decreed that bishops should convene in biannual synods within every province to act as a court of second instance and review cases with excommunication sentences pronounced by individual bishops. But, there was no appeal to a court of final instance "if an unjust sentence was imposed" by a provincial synod acting as a court of second instance. Nicaea I canon 5 "implied that" provincial synods "had an acknowledged authority to" judge the acts of individual bishops of their province. Provincial synods' authority "was becoming well established in the East" prior to the council of Serdica. In 341, the Synod of Antioch canons 14 and 15 "were designed both to augment the authority of the provincial synod as a trial court and to ensure the integrity of its operation." Athanasius of Alexandria was deposed and excommunicated by Eusebians at the first Synod of Tyre (Tyre I) in 335. Athanasius was exiled from Egypt in 339. Athanasius appealed the Tyre I sentence to Julius I. Julius I summoned the Eastern bishops to Rome in 340 to review the Tyre I sentence. The Eastern bishops rejected the review of the Tyre I sentence and formulated a new creed at the Synod of Antioch in 341. Constans I and Julius I commissioned Bishop Hosius of Cordova, who previously presided over Nicaea I, to preside over the council. Hosius and other bishops desired final judgments in the cases of Athanasius and other bishops who had been alternately condemned and vindicated by councils in the East and the West. They also desired to definitively settle the confusion arising from the many doctrinal formulas in circulation, and suggested that all such matters should be referred to an ecumenical council. In order to make the council thoroughly representative, Serdica was chosen as the meeting location. In 340 Athanasius of Alexandria was expelled from his diocese by the Arians. After spending three years in Rome, Athanasius went