The –ParthianWarof–Roman–Parthian War of 161–166 (also called the Parthian War of Lucius Verus) was fought between the Roman and Parthian Empires over Armenia and Upper Mesopotamia. It concluded in 166 after the Romans made successful campaigns into Lower Mesopotamia and Media and sacked Ctesiphon, the Parthian capital.
Origins to Lucius' dispatch, 161–162
On his deathbed in the spring of 161, Emperor Antoninus Pius had spoken of nothing but the state and the foreign kings who had wronged him. One of those kings, Vologases IV of Parthia, made his move in late summer or early autumn 161. Vologases entered the Kingdom of Armenia (then a Roman client state), expelled its king and installed his own—Pacorus, an Arsacid like himself. At the time of the invasion, the governor of Syria was Lucius Attidius Cornelianus. Attidius had been retained as governor even though his term had ended in 161, presumably to avoid giving the Parthians the chance to wrong-foot his replacement. The governor of Cappadocia, the front-line in all Armenian conflicts, was Marcus Sedatius Severianus, a Gaul with much experience in military matters. But living in the east had a deleterious effect on his character.
Alexander of Abonutichus, a prophet who carried a snake named Glycon around with him, had enraptured Severianus, as he had many others. Father-in-law to the respected senator Publius Mummius Sisenna Rutilianus, then-proconsul of Asia, Abonutichus was friends with many members of the east Roman elite. Alexander convinced Severianus that he could defeat the Parthians easily, and win glory for himself. Severianus led a legion (perhaps the IX Hispana) into Armenia, but was trapped by the great Parthian general Chosrhoes at Elegeia, a town just beyond the Cappadocian frontiers, past the headwaters of the Euphrates. Severianus made some attempt to fight Chosrhoes, but soon realized the futility of his campaign, and committed suicide. His legion was massacred. The campaign had only lasted three days.
There was threat of war on other frontiers as well—in Britain, and in Raetia and Upper Germany, where the Chatti of the Taunus mountains had recently crossed over the limes. Marcus Aurelius, who had become emperor on Pius' death on 7 March 161, was unprepared. Pius seems to have given him no military experience; the biographer writes that Marcus spent the whole of Pius' twenty-three-year reign at the emperor's side—and not in the provinces, where most previous emperors had spent their early careers. Marcus made the necessary appointments: Marcus Statius Priscus, the governor of Britain, was sent to replace Severianus as governor of Cappadocia, and was in turn replaced by Sextus Calpurnius Agricola.
More bad news arrived: Attidius Cornelianus' army had been defeated in battle against the Parthians, and retreated in disarray. Reinforcements were dispatched for the Parthian frontier. Publius Julius Geminius Marcianus, an African senator commanding X Gemina at Vindobona (Vienna), left for Cappadocia with vexillations from the Danubian legions. Three full legions were also sent east: I Minervia from Bonn in Upper Germany, II Adiutrix from Aquincum, and V Macedonica from Troesmis. The northern frontiers were strategically weakened; frontier governors were told to avoid conflict wherever possible. Attidius Cornelianus himself was replaced by M. Annius Libo, Marcus' first cousin. He was young—his first consulship was in 161, so he was probably in his early thirties—and, as a mere patrician, lacked military experience. Marcus had chosen a reliable man rather than a talented one.
Marcus took a four-day public holiday at Alsium, a resort town on the Etrurian coast. He was too anxious to relax. Writing to his former tutor Marcus Cornelius Fronto, he declared that he would not speak about his holiday. Fronto replied ironically: "What? Do I not know that you went to Alsium with the intention of devoting yourself to games, joking and complete leisure for four whole days?" He encouraged Marcus to rest, calling on the example of his predecessors (Pius had enjoyed exercise in the palaestra, fishing, and comedy), going so far as to write up a fable about the gods' division of the day between morning and evening—Marcus had apparently been spending most of his evenings on judicial matters instead of leisure. Marcus could not take Fronto's advice. "I have duties hanging over me that can hardly be begged off," he wrote back. Marcus put on Fronto's voice to chastise himself: "'Much good has my advice done you', you will say!" He had rested, and would rest often, but "—this devotion to duty! Who knows better than you how demanding it is!"