An increasingly popular Nontrinitarian Christological doctrine that spread throughout the Roman Empire from the 4th century onwards was Arianism, founded by the Christian presbyter Arius from Alexandria, Egypt, which taught that Jesus Christ is a creature distinct from and subordinate to God the Father. Arian theology holds that Jesus Christ is the Son of God, who was begotten by God the Father with the difference that the Son of God did not always exist but was begotten within time by God the Father, therefore Jesus was not co-eternal with God the Father.

Although the Arian doctrine was condemned as heresy and eventually eliminated by the State church of the Roman Empire, it remained popular underground for some time. In the late 4th century, Ulfilas, a Roman Arian bishop, was appointed as the first Christian missionary to the Goths, the Germanic peoples in much of Europe at the borders of and within the Roman Empire. Ulfilas spread Arian Christianity among the Goths, firmly establishing the faith among many of the Germanic tribes, thus helping to keep them culturally and religiously distinct from Chalcedonian Christians.