Luckily the mutiny of 588 did not ruin the empire; the troops returned to duty when their grievance was removed, and won more victories over the Persians. Hormisdas grew unpopular with his subjects, and was deposed and slain by a usurper named Varahnes. His young son, Chosroes, fled to the Roman camp, and threw himself on the mercy of his hereditary foe. This led to the end of the war; Maurice lent the young prince supplies and auxiliaries to start a rebellion against Varahnes. [Sidenote: Persian War ended, 591.] The rising succeeded, and the grateful Chosroes made peace with the empire the moment that he was restored to his father’s throne (591). The terms, like those of the peaces of 532 and 562, amounted to little more than the restoration of the state of things which had preceded hostilities. Maurice recovered the lost fortresses of Daras and Martyropolis, and gained the Christian districts of Persarmenia, a new acquisition to the empire, but not one of much importance. But the troubles of Maurice, military and financial alike, did not cease with the end of the Persian war. The faithless Avars, disregarding the terms of peace which they had sworn to Tiberius II. in 581, were once more ravaging the Balkan peninsula. In the second year of Maurice’s reign they burst over the Danube, and seized the fortresses of Singidunum and Viminacium, whose garrisons had been reduced by the needs of the Persian war. Unable to raise a new army, Maurice sent them a subsidy which kept them quiet for two years, but in 585 the Tartar horde took arms once more, and threw themselves upon Thrace. Nor was it only with the wild Avars that Maurice had to deal. We now hear of the Slavs as becoming for the first time a serious danger to the empire. Their tribes had for some time dwelt in obscurity along the lower Danube and in the South-Russian plains, having flooded in to occupy the void space left by the migration of the Goths in the fourth century. At the accession of Maurice some of them were subject to the Avars, others were still independent, but all showed a tendency to move southward over the Danube. The Slavs were individually not very dangerous enemies to the empire; they were in the very lowest stage of civilisation, hardly yet accustomed to till the soil, and living the precarious life of fishers and hunters. They did not fight in the open field, but lurked in forests and morasses, issuing forth to plunder by night, and only attacking their foes when they could take them by surprise. It is said that they practised the curious stratagem of lying hid in shallow pools, showing nothing above the surface of the water save the point of a hollow reed, through which they breathed. The story sounds improbable, but Byzantine authors quote several occasions on which it was actually used.