Varro also threw out his light troops in advance. He had sixty-five thousand foot and seven thousand horse, to Hannibal’s thirty-two thousand foot and ten thousand horse. He could not overlap Hannibal’s flanks, so he determined to make his line heavier, and seek to crush him at the first impact. He changed the formation of the maniples so as to make them sixteen men deep and ten men front, instead of sixteen men front by ten deep, as usual. This was a grievous error. His men were unapt to manœuvre or fight well in this unwonted form. He should have employed his surplus, say twenty-five thousand men, as a reserve for emergencies. His army was in the usual three lines, fifteen legions in all, the Roman on the right, the allied on the left. The intervals between the maniples always equalled their front, and the distance between the lines the depth of the maniples. The Roman cavalry, twenty-four hundred strong, was on the right. The allied, forty-eight hundred strong, on the left. It would have been better massed in one body. But such was the only formation then known. Æmilius commanded the right, Varro the left wing. Hannibal placed on his left, opposite the Roman cavalry, his heavy Spanish and Gallic horse, eight thousand strong, two-thirds in a first, and one-third in a second line. This body was strong enough to crush the Roman horse, and thus cut off the retreat of the legions to their camps and towards Rome. In other words, Hannibal’s fighting was to be forced on the Romans’ strategic flank. He had a perfectly lucid idea of the value of a blow from this direction. On his right, facing the allied cavalry, were his Numidians, two thousand strong. Of the infantry, the Spaniards and Gauls were in the centre in alternate bodies. His best troops, the African foot, he placed on their either flank. He expected these veterans to leaven the whole lump. The foot was all in phalanxes of one thousand and twenty-four men each, the African foot in sixteen ranks, as usual, the Spaniards and Gauls in ten. Hannibal had been obliged thus to make his centre thin, from lack of men, but he had seething in his brain a manœuvre by which he proposed to make this very weakness a factor of success. He had been on the ground and had seen Varro strengthen the Roman centre. This confirmed him in his plan. Hannibal commanded the centre in person, Hanno the right, Hasdrubal the left, Maharbal the cavalry of the left. Hannibal relied on Maharbal to beat the Roman cavalry, and then, riding by the rear of the Roman army, to join the Numidians on the Carthaginian right, like Coenus at the Hydaspes. His cavalry was superior in numbers, and vastly outranked in effectiveness the Roman horse.