Valens's mobile forces were tied down in the east, on the Persian frontier (Valens was attempting to withdraw from the harsh terms imposed by Shapur and was meeting some resistance on the latter's part). This meant that only limitanei units were present to oversee the Goths' settlement. The small number of imperial troops present prevented the Romans from stopping a Danube crossing by a group of Ostrogoths and yet later on by Huns and Alans. What started out as a controlled resettlement might any moment turn into a major invasion. But the situation was worsened by corruption in the Roman administration, as Valens' generals accepted bribes rather than depriving the Goths of their weapons as Valens had stipulated and then proceeded to enrage them by such exorbitant prices for food that they were soon driven to the last extremity. Meanwhile, the Romans failed to prevent the crossing of other barbarians who were not included in the treaty. In early 377 the Goths revolted after a commotion with the people of Marcianopolis, and defeated the corrupt Roman governor Lupicinus near the city at the Battle of Marcianople. After joining forces with the Ostrogoths under Alatheus and Saphrax who had crossed without Valens' consent, the combined barbarian group spread out to devastate the country before combining to meet Roman advance forces under Traianus and Richomeres. In a sanguinary battle at Ad Salices, the Goths were momentarily checked, and Saturninus, now Valens' lieutenant in the province, undertook a strategy of hemming them in between the lower Danube and the Euxine, hoping to starve them into surrender. However, Fritigern forced him to retreat by inviting some of the Huns to cross the river in the rear of Saturninus's ranged defenses. The Romans then fell back, incapable of containing the irruption, though with an elite force of his best soldiers the general Sebastian was able to fall upon and destroy several of the smaller predatory bands. By 378, Valens himself was ready to march west from his eastern base in Antioch. He withdrew all but a skeletal force—some of them Goths—from the east and moved west, reaching Constantinople by 30 May, 378. Valens' councillors, comes Richomeres, and his generals Frigeridus and Victor cautioned Valens to wait for the arrival of Gratian with his troops from Roman Gaul, fresh from defeating the Alemanni, and Gratian himself strenuously urged this prudent course in his letters. But meanwhile