Battle of Milvian Bridge

Battle in 312 CE between Maxentius and Constantine in Italy over control of the empire. After experiencing Christian visions, Constantine went on to defeat his rival and become emperor.

Council of Nicaea

Held in Western Asia Minor under Constantine's supervision in 325 CE, a Church council called to sort out the Arian dispute regarding the relationship between Christ and God in terms of degrees of divinity. Though the Orthodox creed was established proclaiming the co-equality of divinity, many were not convinced, Arianism continued, and even became the East's official creed for a time.

Battle of Adrianopole

Battle between Eastern Roman forces led by Valens and Visigothic and Ostrogothic forces in 378 CE. At the battle, Valens refused to wait for reinforcement led by the Western Roman Emperor Gratian, and attacked. The Romans were routed, Valens was killed, and the Eastern army was decimated. The aftermath was large-scale settlement of Goths within Roman lands.

Battle of Catalaunian Plains

A 451 CE battle in central Gaul, in which Barbarian troops, with a small Roman contingent, defeated the forces of Attila the Hun. Overall command was held jointly by Aetius and Theodoric the Visigoth, who died here.