Guard. Had more time had been available, the Urban Prefect of Rome, Marius Maximus, might have been able to muster troops to send as reinforcements to assist Macrinus. Despite their relative powerlessness, the Senate still declared war against the usurper and his family. Battle Descriptions of the battle differ, and its location is debated. The decisive and perhaps sole engagement took place on 8June 218; Dio places it at a defile outside of a village believed to be Immae, approximately twenty-four miles or so by road between Antioch and Beroea. Herodian challenges this assertion, suggesting that the battle took place closer to the borders of Syria Coele and Syria Phoenice, possibly near Emesa. Downey then suggests that two battles took place: an initial engagement matching the one described by Herodian, and a later battle near Antioch, which Downey agrees was the decisive point in the rebellion. Other historians either support Dio's suggested site near Antioch or make no claim with regards to the location of the engagement. Elagabalus' armies, commanded by the inexperienced but determined Gannys, engaged Macrinus' Praetorian Guard in a narrowly fought pitched battle. Gannys commanded at least two full legions and held numerical superiority over the fewer levies that Macrinus had been able to raise. Nonetheless, the engagement began in Macrinus' favour. According to Dio, Macrinus had ordered the Praetorian Guard to set aside their scale armour breastplates and grooved shields in favour of lighter oval shields prior to the battle. This made them lighter and more manoeuvrable and negated any advantage the legionary lanciarii (javelin-armed light infantry) had. The Praetorian Guards broke through the lines of Gannys' force, which turned to flee. 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. These actions effectively ended the retreat; the troops resumed the assault with renewed morale, turning the tide of battle. Fearing defeat, Macrinus fled back to the city of Antioch. Both Downey and Gibbon suggest that had Macrinus not fled, he might have eventually gained victory and secured his position as emperor. Aftermath 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. News of Macrinus' defeat spread and many civilians who had supported him were slain in the city and on