Constantius II

Constantius II tends to be eclipsed by his towering father, Constantine the Great, and by his cousin Julian, who later rejected Christianity. Peter Crawford argues that Constantius was a capable ruler who held power through a dangerous and turbulent period.

When Constantine I died in 337, Constantius, then twenty, and his brothers Constans and Constantine II were each named Augustus and ruled as equal co-emperors. Constantine II died in 340 during a civil war with Constans. For the following decade, Constans and Constantius split the Empire, Constantius governing Egypt and the eastern provinces, where the Sassanid Persian Empire was a constant menace. In 350 the usurper Magnentius killed Constans. Constantius would not accept the situation, went to war against Magnentius, and beat him at the battles of Mursa Major and Mons Seleucus. Magnentius took his own life.

With the rivals gone, Constantius became sole ruler, but he inherited an empire under pressure from many sides. He had some success against the Germanic Alamanni along the Rhine and against the Quadi and Sarmatians beyond the Danube, while his campaigns against Persia produced more mixed outcomes. In 360 he raised his cousin Julian to Caesar, a deputy emperor, and gave him charge of the West so that Constantius could focus on Persia. Julian beat the Alamanni, but his troops then declared him Augustus. As Constantius marched back to confront this challenge to his authority, he fell ill and died. His final act was an effort to prevent another civil war by naming Julian his lawful successor.