When Corbulo had heard all this from messengers he could trust, he sent two legions under Verulanus Severus and Vettius Bolanus to the support of Tigranes, with secret instructions that they were to conduct all their operations with deliberation rather than despatch, as he would prefer to sustain rather than to make war. And indeed he had written to the emperor that a general was wanted specially for the defence of Armenia, and that Syria, threatened as it was by Vologeses, was in yet more imminent peril. Mean- while he posted his remaining legions on the bank of the Euphrates, armed a hastily collected force of provincials, and occupied with troops the enemy's approaches. And as the country was deficient in water, he established forts to guard the wells, and concealed some of the streams with heaps of sand.