could not long hold their conquest. They were beaten and driven out by the native tribes. Byzantium, however, got no relief. The citizens were ground down by payments which had now to be made to their Thracian neighbours. In their distress they begged the Greeks to help them, and, to augment their heavily burdened revenue, they taxed, more rigorously perhaps than ever in the past, every ship which entered the waters of the Euxine.
New complications now arose. All the mercantile world complained bitterly of the loss and inconvenience which Byzantium was inflicting on it. Rhodes was at this time the chief maritime power, and to Rhodes the aggrieved merchants carried their complaints and appealed for redress. First of all, the Rhodians sent an embassy to Byzantium, asking for some remission of the dues. This was refused, and war was then declared against the city about 220 B.C. Rhodes found a useful ally in Prusias, king of Bithynia, to whose court the great Hannibal, some years afterwards, fled as a refugee. Prusias was a powerful prince; he was strong enough to discomfit a host of Gauls which had crossed into Asia on the invitation of Attalus, king of Pergamus, and even to give efficient aid to the Macedonian Philip in his war with Rome. As Prusias was the ally of Rhodes, so was Attalus of the Byzantines. They had hopes, too, of aid from Achaeus, who ruled an extensive dominion in Asia Minor, roughly described by Polybius as the entire country west of the Taurus range. The war began unfavourably for them. Prusias took one of their most
