When Diocletian ascended the throne of the Caesars on September 17, 284, there was still in the field against him an army under the command of Carinus, the elder son of Carus. Carinus was killed by one of his own officers in the battle of the Margus (285), and Diocletian was thus left undisputed master of the Empire. Of all the emperors who up till now had reigned in Rome none had succeeded in emancipating himself so completely from outside influence, whether wielded by the Senate or by the Praetorian Prefect or by any one else, as did this native of Illyria. It was left for him to deprive the Senate of the last of its fictitious prerogatives—prerogatives which had extended even into the domain of army administration—and to become in the fullest sense of the term the founder of an absolute monarchy.