The Roman emperor Caracalla, wanted to make use of this civil war for a conquest of the East and attacked the Parthians in 216. He crossed the Tigris and destroyed the towns, but when Artabanus advanced at the head of an army, he retired to Carrhae. There he was murdered by Martialis on April 8, 217. Caracalla's successor, the Praetorian Prefect of the Guard Macrinus, was defeated at Nisibis and in a peace with Artabanus he gave up all the Roman conquests and paid a heavy contribution to the Parthians. 