The decisive step was taken in the late summer of 572 when, without warning, Marcianus,[1] a first cousin of the Emperor on his mother's side, invaded Arzanene. Justin had given orders for an immediate attack on Nisibis, but precious time was wasted in fruitless negotiations with the Persian marzpan, while Chosroes was informed of the danger, Nisibis victualled and the Christians expelled. Very early in 573 Marcianus, at the head of troops raised from Rome's Caucasian allies, won some slight successes, but dispatches from the capital insisted on the immediate investment of Nisibis; the army encamped before the city at the end of April 573. The Emperor however, suspecting his cousin's loyalty, appointed Acacius Archelaus[2] as his successor. Although Nisibis was about to capitulate, the new commander on his arrival brutally overthrew the tent and standard of Marcianus, while the general himself with rude violence was hurried away to Dara. The army, thinking itself deserted, fled in wild confusion to Mardes, while Chosroes, who had hastened to relieve Nisibis, now advanced to besiege Dara. At the same time Adarmaanes marched into the defenceless province of Syria, captured Antioch, Apamea, and other towns, and rejoined Chosroes with a train of 292,000 prisoners. After an investment of more than five months, on 15 Nov. 573, Dara fell through the negligence or treachery, men said, of John, son of Timostratus. The city had been regarded as impregnable; men seeking security in troublous times had made it the treasure house of the Roman East, and the booty of the victors was immense.
On the news of this terrible disaster Justin ordered the shops to be shut and all trade to cease in the capital; he himself never recovered from the shock, but became a hopeless and violent imbecile. It seems that for five years (presumably since 569) Justin had been ailing and suffering from occasional mental weakness, but it was now clear that he was quite incapable of managing the Empire's affairs. Through the year 574 the Empress in concert with Tiberius, the comes excubitorum, carried on the government. They were faced with a difficult problem: Rome had been the aggressor, could she be the first to propose terms of peace? Persia however intervened, and sent a certain Jakobos, who knew both Greek and Persian, to conclude a treaty. Rome, Chosroes argued, could not be further humbled: she must accept the victor's conditions. The letter was sent to the Empress owing to Justin's incapacity, and it was her reply that Zacharias bore to the Persian court.[3] Rome would pay 45,000 nomismata (metal value about £25,000) to secure peace for a year in the East, though Armenia was not included in this arrangement. If the Emperor recovered, a plenipotentiary should be sent to
