In his haste, he did not first establish supply dumps or short, defendable supply lines, and that later told heavily against him. The Romans arrived in force at the foot of Caros’ Camp, made a series of unsuccessful attempts to storm it, then settled in for a siege. They threw up a double palisade to trap the besieged and to protect their rear, and began the slow process of building a ramp of rocks and packed dirt, planning to drag a tower up it as an archers’ platform to fire down into the fortress. At the same time, Maximian’s engineers began mining through the earthwork walls to breach them from the opposite side of the hill. Arthur, however, had anticipated his rival’s moves, and fought off the engineers and miners. He also had expected a long siege and had scorched the earth for miles around, destroying crops and driving off beasts so the Romans could not live off the land, and the loss of the cargo fleet Grimr had burned meant he could not supply from Gaul. Additionally, the British cavalry forces in nearby Ilchester raided widely, cutting Roman communications, intercepting their supply trains and keeping the Romans largely confined to their own siege camp.
