Editing Maximian (section)

===Failed expedition against Carausius===
[[File:Antoninianus Carausius leg4-RIC 0069v.jpg|thumb|right|Carausius, rebel emperor of [[Roman Britain]]. Legend: IMP. CARAVSIVS P. F. AVG. / LEG IIII FL – ML (Londinium mint)]]

By 289, Maximian was prepared to invade [[Carausius]]' Britain, but for some reason the plan failed. Maximian's panegyrist of 289 was optimistic about the campaign's prospects, but the panegyrist of 291 made no mention of it.{{sfn|Southern|2001|p=143}} Constantius' panegyrist suggested that his fleet was lost to a storm,<ref>''Panegyrici Latini'' 8(5)12.2</ref> but this might simply have been to diminish the embarrassment of defeat.{{sfnm|1a1=Southern|1y=2001|1p=143|2a1=Williams|2y=1997|2p=55}} Diocletian curtailed his Eastern province tour soon after, perhaps on learning of Maximian's failure.{{sfnm|1a1=Potter|1y=2004|1p=285|2a1=Southern|2y=2001|2p=144}} Diocletian returned in haste to the West, reaching Emesa by 10 May 290,<ref>''Codex Justinianus'' 9.41.9</ref> and Sirmium on the Danube by 1 July 290.<ref>''Codex Justinianus'' 6.30.6</ref>{{sfnm|2a1=Barnes|2y=1982|2p=52|1a1=Potter|1y=2004|1pp=285, 650}}

Diocletian met Maximian in Milan either in late December 290 or January 291.{{sfnm|1a1=Barnes|1y=1981|1p=8|2a1=Potter|2y=2004|2p=285}} Crowds gathered to witness the event, and the emperors devoted much time to public pageantry.<ref>''Panegyrici Latini'' 11(3)10, quoted in {{harvnb|Williams|1997|p=57}}.</ref> Potter, among others, has surmised that the ceremonies were arranged to demonstrate Diocletian's continuing support for his faltering colleague. The rulers discussed matters of politics and war in secret,{{sfnm|1a1=Barnes|1y=1981|1p=8|2a1=Potter|2y=2004|2pp=285, 288|3a1=Rees|3y=2002|3p=69}} and they may have considered the idea of expanding the imperial college to include four rulers (the [[Tetrarchy]]).{{sfnm|1a1=Potter|1y=2004|1p=285|2a1=Rees|2y=2002|2p=69}} Meanwhile, a deputation from the Roman Senate met with the rulers and renewed its infrequent contact with the imperial office.<ref>''Panegyrici Latini'' 11(3)2.4, 8.1, 11.3–4, 12.2</ref>{{sfnm|1a1=Barnes|1y=1981|1p=8, 288|2a1=Potter|2y=2004|2pp=285, 650}} The emperors would not meet again until 303.{{sfn|Potter|2004|p=285}}

Following Maximian's failure to invade in 289, an uneasy truce with Carausius began. Maximian tolerated Carausius' rule in Britain and on the continent but refused to grant the secessionist state formal legitimacy. For his part, Carausius was content with his territories beyond the Continental coast of Gaul. Diocletian, however, would not tolerate this affront to his rule. Faced with Carausius' secession and further challenges on the Egyptian, Syrian, and Danubian borders, he realized that two emperors were insufficient to manage the Empire.{{sfn|Williams|1997|p=55–56, 62–64}} On 1 March 293 at Milan, Maximian appointed Constantius to the office of ''Caesar''.{{sfnm|1a1=Barnes|1y=1981|1pp=8–9|2a1=Barnes|2y=1982|2p=4, 36–38|3a1=Potter|3y=2004|3p=288|4a1=Southern|4y=2001|4p=146|5a1=Williams|5y=1997|5pp=64–65}} On either the same day or a month later, Diocletian did the same for [[Galerius]], thus establishing the "Tetrarchy", or "rule of four". Constantius was made to understand that he must succeed where Maximian had failed and defeat Carausius.{{sfnm|1a1=Barnes|1y=1981|1pp=8, 15|2a1=Williams|2y=1997|2p=71}}