How a desperate Roman civil war ended with the rise of a sole emperor
In 388, the Roman world fractured under the weight of competing emperors. Magnus Maximus, a usurper from Britain, faced the disciplined, multi-ethnic forces of Theodosius I. The resulting clash at Poetovio was not merely a tactical engagement but a pivotal moment that consolidated power over the entire Roman Empire.
The conflict originated in 383 when Magnus Maximus was proclaimed emperor in Roman Britain. After the desertion and murder of the Western Emperor Gratian, Maximus expanded his control. By 387, he invaded Italy, forcing the young Valentinian II to flee to Salonica. There, Valentinian sought the protection of Theodosius I, the Eastern Emperor. Theodosius, choosing to support the legitimate heir, spent time assembling a diverse military force composed of Alans, Goths, Huns, and Armenians.
The campaign against Maximus was a two-pronged strategy. Theodosius successfully navigated a naval attack and secured a victory at Siscia, where his cavalry decimated Maximus's forces. This momentum carried him to Poetovio, where he confronted an army led by Marcellinus, the brother of Maximus. The battle was intense, with infantry fighting in squares and cavalry forces effectively neutralizing one another. Maximus's troops fought with intense desperation, yet they were ultimately overwhelmed by the infantry of Theodosius.
Following his defeat at Poetovio, Maximus retreated to the fortress of Aquileia. Theodosius pursued him swiftly, leading to a siege that ended in the surrender of the garrison and the capture of Maximus. His execution on August 28, 388, alongside the death of his son Victor, effectively concluded the civil war. With his rivals eliminated, Theodosius emerged as the sole ruler of the Roman world, spending the years 388 to 391 in Italy to secure the support of the Roman nobility.
Source: Battle of Poetovio
