Macrinus was Emperor of Rome from 217 - 218 A.D succeeding Caracalla after he was assasinated. Previously the praefect of the Praetorian guard, the protector of the Emperor, it is questioned whether or not he had a role in the murder of Caracalla. Nevertheless he became Emperor by self appointment and was later confirmed by the senate. The military gains that Caracallas made against the Parthian Empire were lost. When Macrinus tried to reduce the pay of the troops, a rival Emperor, Elagabalus was found who had the bloodline of Severus. Even though he was only a boy, powerful forces rallied around him. In a quick conflict, Macrinus was defeated and killed and Elagabalus took his place as Emperor.