Caracalla was stabbed in 217 in a plot by his own prefect

The Roman emperor Caracalla was stabbed to death on 8 April 217, on the road from Edessa to Carrhae in Mesopotamia, four days after his 29th birthday. The killer was a soldier named Julius Martialis; the man behind him, according to the contemporary historian Cassius Dio, was Caracalla’s own praetorian prefect, Macrinus, who became emperor within days.

Who really killed Caracalla?

Martialis struck the blow, but Dio — a senator who lived through the reign — describes a plot. Macrinus, fearing for his own life, enlisted two tribunes of the praetorian guard and Martialis, a veteran recalled to service who bore a grudge because Caracalla had refused to make him a centurion. When the emperor dismounted by the road to relieve himself, Martialis approached as if to speak and stabbed him with a small dagger.

He nearly got away. Because he kept hold of his weapon, one of Caracalla’s Scythian bodyguards recognised him and brought him down with a javelin — conveniently silencing the only witness who could name the plotters. Macrinus then took the throne as the first emperor who was neither a senator nor from a senatorial family. He lasted barely a year: Caracalla’s Syrian relatives raised the teenage Elagabalus against him, and after defeat near Antioch on 8 June 218 Macrinus was executed.

Was Caracalla’s citizenship grant an act of generosity?

Dio did not think so. The Constitutio Antoniniana of 212 made all free residents of the empire Roman citizens, and modern scholars see it as a step toward a more uniform state. But Dio wrote that Caracalla’s “real purpose was to increase his revenues”, because non-citizens had escaped most of the taxes he had just raised — including doubling the levy on inheritances and freeing slaves from 5% to 10%.

Dio’s hostility colours everything he wrote about Caracalla, who had also murdered his brother Geta in 211. Even so, his is the only detailed account by someone alive at the time. For a far more famous imperial murder, see the assassination of Julius Caesar.