It's uncertain exactly how Magnus Maximus came to power. At the time he was a general in Britain and whether by his own will or that of his troops he was hailed as emperor. Gratian moved quickly to put down the revolt and bring Maximus to justice but, his troops mutinied, switched sides and had Gratian executed instead. Maximus then sought to have his claim recognized throughout the rest of the empire and to this end he sent a delegation to the court of Theodosius. If not outright enthusiastic, Theodosius was at least initially cooperative and accepted Maximus. However, the situation changed when Maximus upset the balance of power by intending to appropriate Italy which was under the control of Valentinian II. Suddenly, Theodosius realized that Maximus was intent on becoming the sole ruler of the West and possibly the East as well. Theodosius then rescinded his recognition of Maximus and sent a large army against him. The two sides met roughly halfway between their courts and Maximus was defeated. Maximus was then captured and executed in Aquileia.
RIC anecdotal (RIC IX pg. 224 note 46) Obv: DNMAXIMVSPFAVS, laurel and rosette-diademed, draped and cuirassed bust right.
Rev: CONCORDIAAVGGGG Exe: I/CONOB, Constantinopolis, helmeted, seated facing, head right, right foot on prow, holding sceptre in left hand, globe in right, lion's heads on throne.
RIC 84b, Cohen 30 Obv: DNMAGMAXIMVSPFAVG; Pearl-diademed, draped and cuirassed bust right.
Rev: VIRTVSROMANORVM; Roma enthroned left, holding globe and scepter.
S 4203 Obv: DNMAGMAXIMVSPFAVG; Pearl diademed bust right
Rev: REPARATIOREIPVB; Magnus Maximus standing facing, head left, with right hand raising kneeling turreted female and holding Victory on globe in left. Lot sold for $38 11/18/01.