Constans I was one of the sons of Constantine the Great, the first Roman emperor to embrace Christianity. He ruled over the western part of the empire from 337 to 350, when he was killed by a usurper.

Constans was born around 323, as the youngest of three brothers. His father, Constantine, had defeated his rivals and unified the empire under his sole rule. In 333, Constantine appointed Constans as caesar, or junior emperor, and gave him the provinces of Italy, Africa, and Illyricum.

When Constantine died in 337, his sons divided the empire among themselves. Constans became augustus, or senior emperor, and inherited his father’s territories. His brother Constantine II took Gaul, Britain, and Spain, while his other brother Constantius II took the eastern provinces.

Constans soon faced a challenge from Constantine II, who wanted to expand his domain. In 340, Constantine II invaded Italy, but was defeated and killed by Constans’s army near Aquileia. This victory secured Constans’s control over the whole western half of the empire.

Constans was a devout Christian and supported the orthodox doctrine of the Trinity against the Arian heresy. He defended Athanasius of Alexandria, a prominent bishop who had been exiled by Constantius II for opposing Arianism. He also issued laws to protect Christians from persecution and to suppress paganism.

Constans also campaigned against the barbarian tribes that threatened his borders. He fought against the Sarmatians in 341 and visited Britain in 343, where he restored Hadrian’s Wall and built forts. He also faced rebellions from some of his governors and generals, whom he executed or replaced.

In 350, Constans was overthrown by Magnentius, a commander of the imperial guard who proclaimed himself emperor in Gaul. Constans tried to flee to Spain, but was caught and killed by Magnentius’s agents near Vicus Helena. His death ended his thirteen-year reign and sparked a civil war with Constantius II.