Constantine I (306-337) initially reigned as a co-emperor within the tetrarchy, then in 312 he defeated his main opponent Maxentius and became the single ruler of the western part of the empire. At the same time Licinius ruled the eastern part of the empire. In 313, having agreed with each other, they proclaimed the toleration of Christianity (Edict of Milan). In 324 he had Licinius executed and as a sole ruler he founded the first Christian dynasty of the Roman Empire, the Constantine dynasty. Convening of the first universal synod of Christianity in Nicaea (today Iznik, Turkey) in 325 is connected to him. It was there where tenets were first postulated as dogmas as well as the first schism in the church took place. It happened because the followers of presbyter Arius, the so-called Arians, thought the persons of God and Christ were not of the same essence but only similar. During the reign of Constantine short wars broke out against the Goths, who were making incursions into the Great Plain (332), and the Sarmatians, who were under the pressure of the Goths (322), in the vicinity of Pannonia.