Diocletian, Roman emperor, 284–313 CE

Although not the watershed once considered, it remains justified to treat Diocletian’s reign (284–305 ce) as the beginning of Late Antiquity. Its length allowed for changes to take root, and the introduction of a ruling college of two Augusti (Diocletian and Maximian) and two Caesares (Galerius and Constantius I, also made sons-in-law) deterred civil wars by creating predictable lines of succession. Even so, serious civil conflicts arose in Gaul, Britannia, and Egypt, while peoples across the Rhine and Danuble required constant attention. The most glorified campaign was against Sasanian Persia (295/6–298/299), concluded by a signal victory celebrated at a joint triumph/jubilee in Rome (303). Diocletian enlarged the army but did not radically transform its structure, concentrating on consolidation. The empire retained its integrity, and evidence for permanent imperial residences is lacking, but Nicomedia emerges as an eastern imperial centre. Better substantiated is the subdivision of provinces, which increased the presence and capacity of the bureaucracy. The fiscal reform (287–) supported the war effort, making extraction predictable and effective (if not necessarily heavier). A new, global coinage was introduced in 294, and the Edict of Maximum Prices (301) set maxima for commodities, likely to contain inflation. Adjudication was supported by the collection and distribution of Rome’s earliest law codes. Among Diocletian’s most fateful legal actions were those against Christians (303–), doing much to shape his legacy. The notion of a “dominate” has been rejected, but Diocletian’s presentation took on novel aspects, and an extension of court ceremonial indicates an elevation of the imperial office. It became formally separated from the person, as shown by Diocletian’s retirement, settling at Spalato (305). By the time Diocletian died in 313, usurpations had thwarted his system, but his own authority remained undisputed, drawn upon by successors.