Maximian

Diocletian appointed Maximian as Caesar (junior emperor) to govern the Western provinces. This was part of Diocletian's reorganization of the empire, creating a dyarchy. Maximian was given the task of suppressing revolts in Gaul and defending the Rhine frontier.

Maximian campaigned against the Bagaudae rebels in Gaul and later against the usurper Carausius in Britain. He failed to defeat Carausius, who established a breakaway empire in Britain and northern Gaul. The campaign demonstrated the limits of Maximian's military success.

Diocletian elevated Maximian to the rank of Augustus, making him co-emperor of the West. Maximian adopted the title Herculius, symbolizing his role as the active, laboring partner to Diocletian's Jovian. This formalized the division of the empire into two halves.

Maximian abdicated as Augustus alongside Diocletian in a coordinated ceremony at Milan. He retired to a villa in Lucania, but his retirement was forced by Diocletian's plan for an orderly succession. Maximian resented his loss of power and later attempted to reclaim the throne.

After multiple failed attempts to regain power, including a rebellion against Constantine, Maximian was captured at Massilia. Constantine spared his life but forced him to commit suicide. Maximian hanged himself, ending the life of the former co-emperor of the Tetrarchy.