In April 307, he attempted to depose his son, but failed and fled to the court of Constantius' successor, Constantine (Maximian's step-grandson and son-in-law), in Trier.

[6][7] Beyond that, the ancient sources contain vague allusions to Illyricum as his homeland,[8] to his Pannonian virtues,[9] and to his harsh upbringing along the war-torn Danube frontier.

[15] The Christian rhetor Lactantius suggested that Maximian shared Diocletian's basic attitudes but was less puritanical in his tastes, and took advantage of the sensual opportunities his position as emperor offered.

[19] Theodora, the wife of Constantius Chlorus, is often called Maximian's stepdaughter by ancient sources, leading to claims by Otto Seeck and Ernest Stein that she was born from an earlier marriage between Eutropia and Afranius Hannibalianus.

With conflict in every province of the Empire, from Gaul to Syria, from Egypt to the lower Danube, Diocletian needed a lieutenant to manage his heavy workload.

[28] The historian William Seston has argued that Diocletian, like heirless emperors before him, adopted Maximian as his filius Augusti ("Augustan son") upon his appointment to the office.

[35] Once the rituals were over, Maximian assumed control of the government of the West and was dispatched to Gaul to fight the rebels known as Bagaudae while Diocletian returned to the East.

[39] The historian David S. Potter suggests that they were more than peasants, seeking either Gallic political autonomy or reinstatement of the recently deposed Carus (a native of Gallia Narbonensis, in what would become southern France): in this case, they would be defecting imperial troops, not brigands.

[41] Maximian has been implicated in a massacre of Coptic Christian troops from the headquarters unit of a legion raised in Thebes at Aucanus in modern Switzerland in early 285, during the preparations for the campaign against the Bagaudae.

"[45] By the end of the year, the revolt had significantly abated, and Maximian moved the bulk of his forces to the Rhine frontier, heralding a period of stability.

[52] In response to the pirate problem, Maximian appointed Mausaeus Carausius, a Menapian from Germania Inferior (southern and western Netherlands) to command the Channel and to clear it of raiders.

[55] Maximian soon heard that Carausius was waiting until the pirates had finished plundering before attacking and keeping their booty himself instead of returning it to the population at large or into the imperial treasury.

[64] This gave him the same status as Carausius – so the clash was between two Augusti, rather than between an Augustus and a Caesar – and, in Imperial propaganda, Maximian was proclaimed Diocletian's brother, his equal in authority and prestige.

[69] As the panegyrist of 289 declares to Maximian: "So it is that this great empire is a communal possession for both of you, without any discord, nor would we endure there to be any dispute between you, but plainly you hold the state in equal measure as once those two Heracleidae, the Spartan Kings, had done.

Their presence provided a ready pool of manpower and prevented the settlement of other Frankish tribes, giving Maximian a buffer along the northern Rhine and reducing his need to garrison the region.

The rulers discussed matters of politics and war in secret,[96] and they may have considered the idea of expanding the imperial college to include four emperors (the Tetrarchy).

[105] Constantius marched up the coast to the Rhine and Scheldt estuaries where he was victorious over Carausius' Frankish allies, taking the title Germanicus maximus.

In 289, the governor of Mauretania Caesariensis (roughly modern Algeria) gained a temporary respite by pitting a small army against the Bavares and Quinquegentiani, but the raiders soon returned.

In 296, Maximian raised an army, from Praetorian cohorts, Aquileian, Egyptian, and Danubian legionaries, Gallic and German auxiliaries, and Thracian recruits, advancing through Spain later that year.

[113] He may have defended the region against raiding Moors[114] before crossing the Strait of Gibraltar into Mauretania Tingitana (roughly modern Morocco) to protect the area from Frankish pirates.

[116] Not content to drive them back into their homelands in the Atlas Mountains – from which they could continue to wage war – Maximian ventured deep into Berber territory.

Apparently wishing to inflict as much punishment as possible on the tribes, he devastated previously secure land, killed as many as he could, and drove the remainder back into the Sahara.

[118] Inscriptions there record the people's gratitude to Maximian, hailing him – as Constantius had been on his entry to London – as redditor lucis aeternae ("restorer of the eternal light").

[119] After his Mauretanian campaign in 299, Maximian returned to the north of Italy, living a life of leisure in palaces in Milan and Aquilea, and leaving warfare to his subordinate Constantius.

Uncomfortable with sole leadership, Maxentius sent a set of imperial robes to Maximian and saluted him as "Augustus for the second time", offering him theoretic equal rule but less actual power and a lower rank.

A deal was struck in which Constantine would marry Maximian's younger daughter Fausta and be elevated to Augustan rank in Maxentius' secessionist regime.

In return, Constantine would reaffirm the old family alliance between Maximian and Constantius, and support Maxentius' cause in Italy but would remain neutral in the war with Galerius.

[134] On 11 November 308, to resolve the political instability, Galerius called Diocletian (out of retirement) and Maximian to a general council meeting at the military city of Carnuntum on the upper Danube.

Constantine soon heard of the rebellion, abandoned his campaign against the Franks, and moved quickly to southern Gaul, where he confronted the fleeing Maximian at Massilia (Marseille).

[141] In addition to the propaganda, Constantine instituted a damnatio memoriae on Maximian, destroying all inscriptions referring to him and eliminating any public work bearing his image.