What happened June 218 AD

However, his downfall was his refusal to award the pay and privileges promised to the eastern troops by Caracalla. He also kept those forces wintered in Syria, where they became attracted to the young Elagabalus. After months of mild rebellion by the bulk of the army in Syria, Macrinus took his loyal troops to meet the army of Elagabalus near Antioch. Despite a good fight by the Praetorian Guard, his soldiers were defeated. Macrinus managed to escape to Chalcedon but his authority was lost: he was betrayed and executed after a short reign of just 14 months. After his father's defeat outside Antioch, Diadumenian tried to escape east to Parthia, but was captured and killed.

Elagabalus was proclaimed emperor by the troops of Emesa, his hometown, who were instigated to do so by Elagabalus's grandmother, Julia Maesa. She spread a rumor that Elagabalus was the secret son of Caracalla.