The bloody civil war that pitted a Roman emperor against a barbarian usurper
Following the death of Constantine I, his sons fractured the Roman Empire through internal power struggles. When a military conspiracy murdered Constans I in 350 AD, a barbarian officer named Magnentius seized the throne. This triggered a brutal three-year conflict that would reshape the leadership of the Roman world forever.
The conflict originated from the unstable division of the Roman Empire among the sons of Constantine I after his death in 337 AD. Constantine II, Constantius II, and Constans I were granted distinct territories, but tensions over seniority and provincial distribution quickly turned violent. Constantine II invaded Italy in 340 AD, only to be killed by his brother Constans' forces. Constans then consolidated power in the west, but his unpopularity with the military eventually led to his downfall.
In 350 AD, a military conspiracy resulted in the death of Constans I, and the army proclaimed Magnentius, a barbarian officer, as the new western emperor. Constantius II, the last surviving son of Constantine I, marched westward to avenge his brother. The war reached a catastrophic turning point at the Battle of Mursa on 28 September 351. This engagement, involving 95,000 soldiers, resulted in 55,000 casualties, marking it as one of the most lethal confrontations in Roman history.
Following his defeat at Mursa, Magnentius retreated to northern Italy and eventually Gaul. Constantius II systematically reclaimed territories, including Africa, Spain, and southern Italy. The final blow occurred at the Battle of Mons Seleucus on 3 July 353, where Constantius defeated Magnentius once more. Magnentius fled to Lugdunum and took his own life on 11 August 353. In the aftermath, Constantius initiated a ruthless purge, ordering the investigation, torture, and execution of those who had supported the usurper.
Source: Roman civil war of 350–353
