Maximian (Latin: Marcus Aurelius Valerius Maximianus; c. 250 c. July 310), nicknamed Herculius, was Roman emperor from 286 to 305. He was Caesar from 285 to 286, then Augustus from 286 to 305. He shared the latter title with his co-emperor and superior, Diocletian, whose political brain complemented Maximian's military brawn. Maximian established his residence at Trier but spent most of his time on campaign. In late 285, he suppressed rebels in Gaul known as the Bagaudae. From 285 to 288, he fought against Germanic tribes along the Rhine frontier. Together with Diocletian, he launched a scorched earth campaign deep into Alamannic territory in 288, refortifying the frontier.

The man he appointed to police the Channel shores, Carausius, rebelled in 286, causing the secession of Britain and northwestern Gaul. Maximian failed to oust Carausius, and his invasion fleet was destroyed by storms in 289 or 290. Maximian's subordinate, Constantius, campaigned against Carausius' successor, Allectus, while Maximian held the Rhine frontier. The rebel leader was ousted in 296, and Maximian moved south to combat piracy near Hispania and Berber incursions in Mauretania. When these campaigns concluded in 298, he departed for Italy, where he lived in comfort until 305. At Diocletian's behest, Maximian abdicated on 1 May 305, gave the Augustan office to Constantius, and retired to southern Italy.

In late 306, Maximian took the title of Augustus again and aided his son, Maxentius, and his rebellion in Italy. 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. At the Council of Carnuntum in November 308, Diocletian and his successor, Galerius, forced Maximian to renounce his imperial claim again. In early 310, Maximian attempted to seize Constantine's title while the emperor was on campaign on the Rhine. Few supported him, and he was captured by Constantine in Marseille. Maximian killed himself in mid-310 on Constantine's orders. During Constantine's war with Maxentius, Maximian's image was purged from all public places. However, after Constantine ousted and killed Maxentius, Maximian's image was rehabilitated, and he was deified.



Diocletian (; Latin: Gaius Aurelius Valerius Diocletianus; c. 242/245 – 311/312), nicknamed Iovius, was Roman emperor from 284 to 305. Born to a family of low status in Dalmatia, originally named Diocles, Diocletian rose through the ranks of the military to become a cavalry commander of the Emperor Carus's army. After the deaths of Carus and his son Numerian on campaign in Persia, Diocletian was proclaimed emperor by the troops. The title was also claimed by Carus's surviving son, Carinus, but Diocletian defeated him in the Battle of the Margus.

Diocletian's reign stabilized the empire and ended the Crisis of the Third Century. He appointed fellow officer Maximian as Augustus, co-emperor, in 286. Diocletian reigned in the Eastern Empire, and Maximian reigned in the Western Empire. Diocletian delegated further on 1 March 293, appointing Galerius and Constantius as junior co-emperors (each with the title Caesar), under himself and Maximian respectively. Under the Tetrarchy, or "rule of four", each emperor would rule over a quarter-division of the empire. Diocletian secured the empire's borders and purged it of all threats to his power. He defeated the Sarmatians and Carpi during several campaigns between 285 and 299, the Alamanni in 288, and usurpers in Egypt between 297 and 298. Galerius, aided by Diocletian, campaigned successfully against Sassanid Persia, the empire's traditional enemy. In 299 he sacked their capital, Ctesiphon. Diocletian led the subsequent negotiations and achieved a lasting and favourable peace.

Diocletian separated and enlarged the empire's civil and military services and reorganized the empire's provincial divisions, establishing the largest and most bureaucratic government in the history of the empire. He established new administrative centres in Nicomedia, Mediolanum, Sirmium, and Trevorum, closer to the empire's frontiers than the traditional capital at Rome. Building on third-century trends towards absolutism, he styled himself an autocrat, elevating himself above the empire's masses with imposing forms of court ceremonies and architecture. Bureaucratic and military growth, constant campaigning, and construction projects increased the state's expenditures and necessitated a comprehensive tax reform. From at least 297 on, imperial taxation was standardized, made more equitable, and levied at generally higher rates.

Not all of Diocletian's plans were successful: the Edict on Maximum Prices (301), his attempt to curb inflation via price controls, was counterproductive and quickly ignored. Although effective while he ruled, Diocletian's tetrarchic system collapsed after his abdication under the competing dynastic claims of Maxentius and Constantine, sons of Maximian and Constantius respectively. The Diocletianic Persecution (303–312), the empire's last, largest, and bloodiest official persecution of Christianity, failed to eliminate Christianity in the empire. After 324, Christianity became the empire's preferred religion under Constantine. Despite these failures and challenges, Diocletian's reforms fundamentally changed the structure of Roman imperial government and helped stabilize the empire economically and militarily, enabling the empire to remain essentially intact for another 150 years despite being near the brink of collapse in Diocletian's youth. Weakened by illness, Diocletian left the imperial office on 1 May 305, becoming the first Roman emperor to abdicate the position voluntarily. He lived out his retirement in his palace on the Dalmatian coast, tending to his vegetable gardens. His palace eventually became the core of the modern-day city of Split in Croatia.