3-13. A New War with Persia
While Julian had been recovering Gaul, Constantius had been engaged in a series of campaigns on the Danube frontier, and for this purpose had removed his court from Milan to Sirmium. An unimportant expedition against the Suevi in Rhaetia in 357 was followed in 358 by lengthy operations in the plains about the Danube and the Theiss against the Quadi and various Sarmatian tribes who had burst plundering across the border. The barbarian territory was ravaged, and through the Emperor's successful diplomacy one people after another submitted and surrendered their prisoners. They were in most cases left in possession of their lands under the supremacy of Rome, but the Limigantes were forced to settle on the left instead of the right bank of the Theiss, while the Sarmatae Liberi were given a king by Constantius in the person of their native prince Zizais, and were themselves restored to the district which the Limigantes had been compelled to leave.
The latter however in the following year (359), discontented with their new homes, craved that they might be allowed to cross the Danube and settle within the Empire. This Constantius was persuaded to permit, hoping thus to gain recruits for the Roman army and thereby to lighten the burdens of the provincials The Limigantes, once admitted upon Roman territory, sought to avenge themselves for the losses of the previous year by a treacherous onslaught upon the Emperor. Constantius escaped and a general massacre of the faithless barbarians ensued. The pacification of the northern frontier was now complete.
Meanwhile in the East hostilities with Persia had ceased on any large scale since 351, and in 356-7 the praefect Musonianus had been carrying on negotiations for peace (through Cassianus, military commander in Mesopotamia) with Tampsapor a neighbouring satrap. But the moment was inopportune. Sapor himself had at length effected an alliance with the Chionitae and Gelani and now (spring 358) in a letter to the Emperor demanded the restoration of Mesopotamia and Armenia; in case of refusal he threatened military action in the following year. Constantius proudly rejected the shameful proposal, but sent two successive embassies to Persia in the hope of concluding an honourable peace. The effort was fruitless.
Court intrigue deprived Ursicinus, Rome's one really capable general in the East, of the supreme command, and in spite of the prayers of the provincials he was succeeded by Sabinianus, who in his obscure old age was distinguished only by his wealth, inefficiency and credulous piety. During the entire course of the war inactivity was the one prominent feature of his generalship. On the outbreak of hostilities in 359 the Persians adopted a new plan of campaign. A rich Syrian, Antoninus by name, who had served on the staff of the general commanding in Mesopotamia, was threatened by powerful enemies with ruin. Having compiled from official sources full information alike as to Rome's available ammunition and stores and the number of her troops he fled with his family to the court of Sapor; here, welcomed and trusted, he counselled immediate action: men had been withdrawn from the East for the campaigns on the Danube, let the King no longer be content with frontier forays, let him without warning strike for the rich province of Syria unravaged since the days of Gallienus!
The deserter's advice was adopted by the Persians. On the advance of their army, however, the Romans, withdrawing from Charrae and the open countryside burned down all vegetation over the whole of northern Mesopotamia. This devastation and the swollen stream of the Euphrates forced the Persians to strike northward through Sophene; Sapor crossed the river higher in its course and marched towards Amida. The city refused to surrender, and the death of the son of Grumbates, king of the Chionitae, provoked Sapor to abandon his attack on Syria and to press the siege. Six legions formed the standing garrison, a force which probably numbered some 6000 men in all. But at the time of the Persian advance the country-folk had all assembled for the yearly market, and when the peasantry fled for refuge within the city walls Amida was densely overcrowded. None however dreamed of surrender; Ammianus, one of the besieged, has left us a vivid account of those heroic seventy-three days. In the end the city fell (6 Oct.) and its inhabitants were either slain or carried into captivity. Winter was now approaching and Sapor was forced to return to Persia with the loss of 30,000 men.
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