What happened 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.

The Battle of the Trebia (or Trebbia) was the first major battle of the Second Punic War, fought between the Carthaginian forces of Hannibal and a Roman army under Sempronius Longus on 22 or 23 December 218 BC.

The Second Punic War, which lasted from 218 to 201 BC, was the second of three wars fought between Carthage and Rome, the two main powers of the western Mediterranean in the 3rd century BC.

In 218 BC, Attalus recaptured his former territories with the help of some Thracian Gauls.