Marcus Aurelius Valerius Maximianus, 286 - 305, 306 - 308, 310 

Appointed as emperor of the west by Diocletian in 286, Maximian ruled his half of the empire for nearly twenty years before reluctantly abdicating with Diocletian, in accordance with the latter's tetrachy system. In 306, Maxentius, son of Maximian, revolted against the legitimate western emperor, Severus II. Maxentius invited his father to reassume his authority as Augustus. Severus met the forces of Maxentius in battle, and was defeated and eventually slain. The emperor of the east, Galerius, made preparations to march on Maxentius. Maximian sought an alliance with the western Caesar, Constantine I , who was raised to the title of Augustus. In 308, however, Maximian quarreled with Constantine and returned to Rome. Galerius called a conference in the same year to settle the emperors' differences without civil war. The former emperor Diocletian also attended. Maximian was forced to abdicate a second time and Constantine was demoted to Caesar. Maximian retired to the court of Constantine , but in 310, he rebelled again and yet again declared himself Augustus. This was his final fling, however, and Constantine defeated and captured him. He was killed or died naturally shortly afterwards.