Parthian war of Caracalla

Events leading up to the war

In the years before the war, Parthia was divided by a conflict between the sons of King Vologases V. Vologases VI succeeded his father in 208, but his brother Artabanus IV rebelled and declared himself king. Artabanus eventually gained the upper hand without fully defeating his brother, and the instability affected the neighbouring kingdoms of Armenia and Osroene, which lay in the buffer zone between the Roman and Parthian empires. Caracalla exploited civil strife in both kingdoms to expand Roman power and set the stage for an advance into Parthia.

According to the Roman historian Cassius Dio, the Osroenean king Abgar IX ruled harshly and aroused discontent. Caracalla used this as a pretext to summon and imprison Abgar, then annexed Osroene as a Roman province. Three years later, Caracalla intervened in a civil conflict between Khosrov I of Armenia and his sons. He offered to mediate but imprisoned the king and his sons, provoking an Armenian uprising that continued at the time of Caracalla's death in 217.

Caracalla travelled to the eastern Mediterranean in 215 and made Antioch his de facto capital. He is reported to have sought to associate himself with Alexander the Great and to have ordered numerous statues of the conqueror. He also travelled to Alexandria in Egypt to pay respects at Alexander's tomb but instead carried out a great massacre of the local population in 215.

Parthian campaign and assassination

In the winter of 215–16, Caracalla based himself in Nicomedia with the Roman army, gearing up for a campaign against Armenia and Parthia. Dio claims Caracalla was hunting for a reason to start a war, and initially latched onto the Parthian king Vologases VI refusing to hand over two hostages. But when Vologases was ousted by his brother Artabanus, the hostages were delivered, killing that excuse. Caracalla then cooked up a new justification, though Dio and Herodian disagree on the details.

Both say Caracalla argued that Artabanus had turned down his request to marry the Parthian king’s daughter. Dio thinks Artabanus refused because he suspected Caracalla would use the marriage to swallow Parthia. Herodian, however, says Artabanus eventually gave in and agreed. At a celebration for Caracalla’s arrival, likely at the Parthian palace in Arbela, Caracalla had his men slaughter the guests.

After that, the Roman army rampaged through Parthia, mostly sticking to northern Mesopotamia and the pro-Parthian kingdom of Adiabene—possibly more of a show of force than a real attempt at conquest. Caracalla wrote to the Senate claiming victory over Parthia and picked up the title Parthicus Maximus, adding it to his Britannicus Maximus and Germanicus Maximus. The army spent the winter in Edessa, but Caracalla was killed on 8 April 217 while relieving himself by the roadside.

The Parthians recovered and fought the Romans to a bloody draw at the Battle of Nisibis. His successor Macrinus wrapped up the war in 218 by paying compensation for the damage Caracalla had caused.