Battle of the Margus

The Battle of the Margus was fought in May 285 between the armies of Roman Emperors Diocletian and Carinus in the valley of the Margus River (today Morava) in Moesia (present day Serbia). The exact circumstances of the battle are in doubt, but it is known for certain that Carinus was killed in the course of the battle, leaving Diocletian in sole control of the Roman Empire. The tide of the battle may have tilted to Carinus at first, only to shift in Diocletian's favor after the defection of Carinus' Praetorian Prefect, Aristobulus. Some scholars suspect that Aristobulus was responsible for the murder of Carinus, an argument that gains credibility in the fact that Diocletian afterward rewarded Aristobulus by confirming him in office as Praetorian Prefect and Consul for the remainder of 285. Although the battle decisively decided the issue of Roman leadership in Diocletian's favor, it is likely that, with the eastern provinces behind him, Diocletian would eventually have outlasted Carinus even if he had found himself on the losing side at Margus. Aristobulus may well have recognized this fact and taken matters into his own hands in order to secure the good graces of the man he perceived to be the inevitable winner. After his victory, Diocletian administered the oath of loyalty to Carinus' former troops, then turned his attention to the Danube frontier where the Marcomanni and Quadi were conducting raids.