remain in control of campaigns simultaneously on more than just one front. After suffering a defeat by the Persians in 296, Galerius crushed Narseh in 298—reversing a series of Roman defeats throughout the century—capturing members of the imperial household and a substantial amount of booty and gaining a highly favourable peace treaty, which secured peace between the two powers for a generation. Similarly, Constantius defeated the British usurper Allectus, Maximian pacified the Gauls, and Diocletian crushed the revolt of Domitianus in Egypt. Demise When in 305 the 20-year term of Diocletian and Maximian ended, both abdicated. Their caesares, Galerius and Constantius Chlorus, were both raised to the rank of augustus, and two new caesares were appointed: Maximinus Daza (caesar to Galerius) and Valerius Severus (caesar to Constantius). These four formed the second tetrarchy. However, the system broke down very quickly thereafter. When Constantius died in 306, Galerius promoted Severus to augustus while Constantine, Constantius' son, was proclaimed augustus by his father's troops. At the same time, Maxentius, the son of Maximian, who also resented being left out of the new arrangements, defeated Severus before forcing him to abdicate and then arranging his murder in 307. Maxentius and Maximian both then declared themselves augusti. By 308 there were therefore no fewer than four claimants to the rank of augustus (Galerius, Constantine, Maximian and Maxentius), and only one to that of caesar (Maximinus Daza). In 308 Galerius, together with the retired emperor Diocletian and the supposedly retired Maximian, called an imperial "conference" at Carnuntum on the River Danube. The council agreed that Licinius would become augustus in the West, with Constantine as his caesar. In the East, Galerius remained augustus and Maximinus remained his caesar. Maximian was to retire, and Maxentius was declared a usurper. This agreement proved disastrous: by 308 Maxentius had become de facto ruler of Italy and Africa even without any imperial status, and neither Constantine nor Maximinus—who had both been caesares since 306 and 305 respectively—were prepared to tolerate the promotion of the augustus Licinius as their superior. After an abortive attempt to placate both Constantine and Maximinus with the meaningless title filius augusti ("son of the augustus", essentially an alternative title for caesar), they both had to be recognised as Augusti in 309. However, four full Augusti all at odds with each other did not bode well for the tetrarchic system. Between 309 and 313 most of