1. Causes and pretexts of the Parthian wars

Historians agree that the main – if not unique – cause of Caracalla’s campaign against the Parthians originated from his unlimited and rather pathological admiration for Alexander the Great and not from any special strategic necessity of the time. Besides, the emperor’s attempt at imitating the Macedonian king and his achievements seems to have determined his entire policy in general.¹

From around 213 AD onwards, there was a civil conflict in Parthia since Artabanus IV had already had Media under his control and was successfully claiming Mesopotamia and the throne from his brother, king Vologases VI. Of course, Caracalla was particularly happy with this turn of events that contributed to the weakening of the traditional enemy and boasted of being the instigator of the internal conflict in the Parthian state.² The following actions that took place around the end of 213 AD-beginning of 214 AD can be considered the prelude to the war and the indication of Caracalla’s intentions. The ruler of the subordinate kingdom of Osroene, Agbar IX (or Abgar), was invited to Rome and imprisoned, whereas his small dominion was annexed to the empire. In Armenia, the usual field of antagonism and conflict between Romans and Parthians, the local king was fighting against his sons. Caracalla invited them to Rome under the pretext of a peace mediation, but they met Agbar’s fate. Despite their leaders’ imprisonment, the Armenians refused to submit and resorted to arms.³

2. Presentation of actions and war events

A little later, the emperor departed for the East. He finally arrived in Thrace and crossed the Hellespont in the autumn of 214 AD.⁴ He visited Ilium, Pergamon,⁵Thyateira⁶ and possibly Philadelphia. Generally speaking, his passage through Asia Minor was accompanied by the granting of neokoria and privileges to various cities, whereas he was honoured and awarded by their citizens in return.⁷ He spent the winter in Nicomedeia and left Bithynia in April 215 AD.⁸ After passing through Galatia, Cappadocia and Cilicia and visiting Tyana,⁹ he arrived in Antioch, his operational base, at the beginning of summer.¹⁰

The army Caracalla had assembled comprised of legions I and II Adiutrix, II Parthica, III Augusta, III Italica, III Cyrenaica, IV Scythica¹¹ and XVI Flavia Firma – not all of them were probably fully manned –¹² 16,000 Macedonians forming a phalanx in imitation of Alexander the Great’s army,¹³ a unit of Spartans¹⁴ and German allied units (auxilia).¹⁵ Caracalla demanded the handing over of the cynic philosopher Antiochus, his former favourite, and Tiridates, probably a contender for the Armenian crown, who had taken refuge in Parthia.¹⁶ Vologases responded to the request and the campaign against him was postponed. At the same time or a little earlier, the emperor sent an expeditionary force to Armenia under the freedman and former dancer Theocritus, who was heavily defeated.¹⁷ It seems, however, rather odd that Caracalla postponed the planned invasion so easily. It is possible that he came to an agreement with the Parthian king or waited for a more favourable outcome of the Parthian civil conflict. So he left for Alexandreia.¹⁸

After his return to Antioch in the spring of 216 AD, Caracalla, under the pretext of uniting the two great powers of the world, asked Artabanus, who must have been recognized as a king by most of his countrymen, for his daughter’s hand in marriage.¹⁹ There is a chance that his proposal was sincere, another attempt at imitating Alexander the Great. However, he probably did it in order to have a plausible casus belli after Artabanus’ expected refusal.²⁰ Whatever Caracalla’s initial intention or Artabanus’ respond,²¹ the emperor finally crossed the Tigris River and invaded Adiabene in the summer/autumn of 216 AD. He seized, plundered and destroyed several fortified villages and cities, whereas his men desecrated the Parthian kings’ tombs in Arbela. Caracalla himself is reported to have given his men absolute freedom to slaughter and plunder. The Parthians did not risk an open battle and retreated without resistance to the highlands in order to assemble their forces. After his easy but of relatively small extent success, Caracalla spent the next months in Mesopotamia,²² mainly in Edessa, preparing the next phase of operations. However, his actions and life came to an unexpected end at the beginning of April 217 AD when he was murdered on the road connecting Edessa and Carrhae after a conspiracy plotted by Macrinus, the commander of the praetorians and his eventual successor.²³

3. Evaluation

In conclusion, and according to the little evidence by the admittedly hostile to Caracalla ancient sources, his Parthian war presents in military terms a rather odd image that seems to be consistent with the emperor’s personality. The operation as a whole is characterized by a relative lack of clear strategy and attempt to achieve its objectives, enigmatic procrastination and occasional distractions, as well as the tragic choice of Theocritus as the commander of the unsuccessful campaign in Armenia.