Parthian war of Caracalla

In the years immediately before the war, Parthia was roiled by a conflict between the two sons of King Vologases V. Vologases VI succeeded his father in 208 but his brother Artabanus IV rebelled and declared himself king soon afterwards. While Artabanus eventually gained the upper hand, though without totally defeating his brother, the conflict destabilised the neighbouring kingdoms of Armenia and Osroene in the buffer zone between the Roman and Parthian Empires. Caracalla exploited civil strife in both kingdoms in order to expand Roman power in the region and set the scene for an advance into Parthia. As Armenia and Osroene were both in the Parthian sphere of influence at this time – Armenia had swung between being either a Roman or a Parthian client state for over a century – he evidently saw an establishment of Roman domination as being a way of reducing Parthian power and positioning himself for an eventual move against Parthia itself. According to the Roman historian Cassius Dio, the Osroenean king Abgar IX aroused discontent among his people by ruling them harshly. Caracalla used this as a pretext to overthrow Abgar, summoning him to a meeting and then imprisoning the king. With Abgar out of the way, Caracalla proceeded to annex Osroene and make it a Roman province. Three years later, he intervened in a civil conflict between Khosrov I of Armenia and his sons. The emperor offered to mediate in their dispute but proceeded to imprison the king and his quarrelling sons, provoking an uprising among the Armenians. The uprising was still ongoing at the time of Caracalla's death in 217. ==Parthian campaign and assassination==

During the winter of 215–16, Caracalla stayed in Nicomedia with the Roman army preparing to launch a campaign against the Armenians and Parthians. According to Dio, Caracalla sought a pretext for war in the refusal by the Parthian king Vologases VI to release a pair of hostages – Tiridates of Armenia and a Cynic philosopher named Antiochus. However, when Vologases was deposed by his brother Artabanus the hostages were sent to Caracalla, temporarily depriving the emperor of a casus belli. Cassius Dio writes: Caracalla subsequently informed the Roman Senate by letter that Parthia had been defeated and was awarded the title of Parthicus Maximus, "great conqueror of Parthia", to go along with his existing titles Britannicus Maximus and Germanicus Maximus (referring to earlier campaigns in Britain and Germany). The army spent the winter at Edessa, but Caracalla was assassinated on 8 April 217 while urinating at a roadside. The Parthians regrouped, fighting the Romans to a bloody standstill at the Battle of Nisibis. His successor, Macrinus, brought the war to an end in 218 by paying the Parthians reparations of possibly as much as 50 million denarii. ==References==