A key reason for some historians' disparagement of the Roman cavalry were the crushing defeats, at the Trebia and at Cannae, that it suffered at the hands of the Carthaginian general Hannibal during the latter's invasion of Rome (218-6 BC) which were only rendered possible because of a powerful cavalry force. But Sidnell argues that this is only because of a consistent numerical superiority in cavalry. Another disadvantage for the Romans in the Second Punic War was that their respective cavalry were melee cavalry better suited for combating enemy melee cavalry and engaging the rear and flanks of infantry formations. This, however useful and effective against the Romans' regular opponents, failed against Hannibal's nimble Numidian light cavalry, whose use of skillful hit and run tactics exasperated the Roman cavalry who were unable to come to grips with them.