Arianism

From Conservapedia

Originating around AD 300, Arianism was the theological view that Jesus was divine, but created and lesser than God the Father. It was considered to be a heresy.

Arianism was officially condemned as incorrect by the Council of Nicaea in 325, which gave its seal of authority to the established trinitarian view. While Arianism continued to be a small issue in the Roman Empire, the biggest influence and conflict due to Arianism was from the barbarian tribes surrounding the Empire. They had generally been Christianized, but mostly with Arianism tendencies.

The barbarian tribes which invaded Rome, and caused its fall in 476, were often Arians. The Visigoths and the Ostrogoths, and especially Theoderic, were followers of the Arian heresy. It would take centuries before the trinitarian view prevailed in those regions.