Europe 287: Carausian Revolt
Diocletian and the Tetrarchy
In 286 Diocletian appointed his deputy Maximian as co-emperor to rule the West while he himself ruled the East. Almost immediately the Germanic tribes invaded Gaul while Frankish and Saxon pirates raided the Channel. To deal with the pirates, Maximian placed the general Carausius in charge of the Channel fleet, but, after being accused of corruption, Carausius fled to Britain with the fleet and proclaimed himself emperor.
The Agri Decumates was lost to the Romans in c.262, regained by Aurelian and Probus in 275–8, and lost again sometime between 290 and 310. The losses here seem not so much due to any rise in power of the local Alemanni tribe, but Roman internal division. When rival Roman factions controlled Gaul and Raetia, as was the case in 262–274 and 306, the limes of the Agri Decumates were no longer defensible and had to be abandoned.
? Jul 285–1 May 305 Reign of Diocletian▲
In 285 the 40-year-old Diocletian assumed complete control of the Roman Empire and the following year appointed his deputy Maximian as Augustus (co-emperor) to reign in the Western Empire, while Diocletian himself reigned on in the East. Over the next twenty years Diocletian vigorously reformed the empire, both by decentralization—he implemented the Tetrarchy (rule of two Augusti and two Caesars) in 293—and increasing bureaucracy and autocracy. In 305 he and Maximian stepped down in favor of the two Caesars, in an attempt to establish a precedent by becoming the first Roman emperor to retire voluntarily.in wikipedia
Nov–Dec 285 Diocletian’s First Sarmatian Campaign▲
While returning to Nicomedia in late 285, Diocletian encountered Germans and Sarmatians in Pannonia, who were seeking new lands within the Roman Empire. This may have been a continuation of the incursions of migrating Sarmatians and Quadi that Carus and Carinus had faced in earlier years. Diocletian defeated the invaders but was unable to eliminate them as a threat due to the onset of winter.in wikipedia
1 Apr 286–1 May 305 Co-reign of Maximian▲
In July 285 Diocletian appointed his slightly younger deputy Maximian as Caesar and the following year promoted him to Augustus (co-emperor). Diocletian took the title Jovius (after Jupiter) and ruled at Nicomedia in the East, while Maximian took the subordinate title Herculius (after Hercules) and ruled from Augusta Treverorum (Trier) in the West. In 293, with the implementation of the Tetrarchy, Maximian moved to Italy and appointed Constantius as his Caesar in Gaul and Britain. When Diocletian abdicated in favor of his own Caesar, Galerius, in 305, Maximian also stepped down, entering a reluctant retirement.in wikipedia
286–288 Maximian’s Rhenish War▲
In the fall of 286, not long after the defeat of the Bagaudae revolt, a number of Germanic tribes—Franks, Saxons, Alemanni, Burgundi, and others—attacked Gaul. Although his situation was complicated by Carausius’ revolt, Maximian defeated the invaders and in 287 crossed the Rhine into Magna Germania to take the fight to the enemy. The next year, in conjunction with his prefect Constantius Chlorus in Lower Germania and his co-emperor Diocletian in Raetia, he launched a second counter-invasion and ultimately forced the Germans to sue for peace.in wikipedia
286? Carausian Revolt▲
To deal with Frankish and Saxon pirates, Maximian placed the general Carausius in charge of the Channel fleet at Bononia (Boulogne-sur-Mer). However, Maximian soon came to believe that Carausius was collaborating with the raiders to enrich himself and sentenced him to death. In response, Carausius proclaimed himself emperor in late 286 or early 287 and fled to Britain with the fleet. Despite this, Carausius seems to have held out hope of being formally acknowledged as a third co-emperor, as he continued to recognize the reigns of Diocletian and Maximian.in wikipedia