At the time of his accession he inherited all of the problems that Caracalla had left for Rome—war against Parthia, threats from Armenia and Dacia, and extensive fiscal expenditures.

Caracalla's aunt, Julia Maesa, his mother's sister, took advantage of the discontent of the soldiers and spent from her wealth to champion her grandson Elagabalus as the rightful heir to the empire.

Elagabalus, chief priest of the god Elagabal, was proclaimed emperor by the soldiers of Legio III Gallica (Gallic Third Legion) at their camp in Raphanea on 16 May 218.

Gannys' troops turned and renewed the assault, causing Macrinus to flee the battle in fear and return to Antioch.

Macrinus' predecessor Caracalla was murdered on April 8, 217, during a period of war with the Parthians, near Carrhae while traveling en route to visit a temple.

[3][4] Martialus was himself cut down by Caracalla's German Guards immediately afterwards, a convenient fact for Macrinus, at the time a praetorian prefect, who was involved in the assassination.

One such dispatch detailed a prophecy, perhaps fabricated, from the oracle at Delphi suggesting that Macrinus was destined to kill Caracalla and succeed him as emperor.

The military at the time was concentrated against the Parthians in the area around Edessa (modern Şanlıurfa, Turkey), so there was no force anywhere in the Empire that could contest the status of Macrinus.

[16] Historian Andrew Scott doubts the credibility of this high figure, noting that Dio's records are frequently unreliable on finances.

[18] With the peace treaty concluded, Macrinus took measures to control the expenditures of Rome, by reversing Caracalla's changes and thus effectively reinstating the fiscal policies of Septimius Severus.

[22] Julia's suspicions regarding Macrinus' involvement in the death of Caracalla led to her championing the case of her grandson, Elagabalus, as the rightful emperor.

[22] On the night of 15 May 218, Elagabalus was taken, by either Julia Maesa or Gannys, to the camp of the Legio III Gallica at Raphanea and presented to the soldiers stationed there.

[22][26] In Gibbon's opinion, Macrinus might have been able to stop the rebellion in this early stage, but failed to contain it because he was unable to decide on an appropriate course of action and instead remained at Antioch.

In response to the growing threat, Macrinus sent out a cavalry force under the command of Ulpius Julianus to try to regain control of the rebel soldiers.

The emperor of Rome was appointed by the support of the military, while the Senate existed solely to officiate state affairs without any real authority.

[13][37] Elagabalus' armies, commanded by the inexperienced but determined Gannys, engaged Macrinus' Praetorian Guard in a narrowly fought pitched battle.

During the retreat, however, Julia Maesa and Soaemias Bassiana (Elagabalus' mother) joined the fray to rally the forces while Gannys charged on horseback headlong into the enemy.

After his defeat, Macrinus sent his son Diadumenian to Artabanus V of Parthia, while he himself returned to Antioch, proclaiming himself victorious over Elagabalus in battle.

Fleeing the city at night on horseback, he reached Cilicia with a few companions, masquerading as a military courier, and secured a carriage to drive to Eribolon, near Nicomedia.

[43][44] French author Jean-Baptiste Crevier comments that Macrinus threw himself out of the carriage at Cappadocia after receiving the news of the death of his son, breaking his shoulder in the act.

History professor and author Martijn Icks notes the irony of Verus' claim as his legion had been the first to proclaim Elagabalus as the rightful emperor of Rome.

[46] By March 222 AD, Elagabalus was himself murdered by the Praetorian Guard, his body dumped in the river Tiber and his memory condemned by damnatio memoriae ordered by the senate.