In 209 b.c. P. Cornelius Scipio captured the city of New Carthage. The victory was crucial for the Roman war effort in Spain, and indeed in Italy too, but Scipio's campaign is especially memorable—and the subject of much debate—on account of the manner in which the city was taken. New Carthage had in effect been built on a peninsula, with the sea to the south and a lagoon to the north, and with a canal joining the two to the west. The city, therefore, could only be approached by land from the east; but, according to Polybius, Scipio had learnt from some fishermen that the lagoon was shallow and could be forded in most places and, moreover, that the waters in it usually receded each evening (10.8.7). It was this knowledge that Scipio exploited to take the city. But this same knowledge he also kept from his men (10.9.1, 10.9.4–5). In his address to his soldiers prior to the attack, Polybius says, Scipio told them that Poseidon had visited him in his sleep and had promised to assist the Romans in their operations in a way that would be apparent to all (10.11.7).
