We know that of Hannibal's infantry only twelve thousand at the most were equipped with Roman weapons. We know that his Gallic and Iberian infantry, protected by plain shields, had to fall back, turn, and probably lost in this part of the action very nearly the four thousand men, which the battle cost them.
Let us deduct the ten thousand men that had gone to the attack of Hannibal's camp and the five thousand which the latter must have left there. There remain:
A mass of seventy thousand men surrounded and slaughtered by twenty-eight thousand foot soldiers, or, counting Hasdrubal's cavalry, by thirty-six thousand men, by half their number.
It may be asked how seventy thousand men could have let themselves be slaughtered, without defense, by thirty-six thousand men less well-armed, when each combatant had but one man before him. For in close combat, and especially in so large an envelopment, the number of combatants immediately engaged was the same on each side. Then there were neither guns nor rifles able to pierce the mass by a converging fire and destroy it by the superiority of this fire over diverging fire. Arrows were exhausted in the first period of the action. It seems that, by their mass, the Romans must have presented an insurmountable resistance, and that while permitting the enemy to wear himself out against it, that mass had only to defend itself in order to repel assailants.
But it was wiped out.
In pursuit of the Gauls and Iberians, who certainly were not able, even with like morale, to stand against the superior arms of the legionaries, the center drove all vigorously before it. The wings, in order to support it and not to lose the intervals, followed its movement by a forward oblique march and formed the sides of the salient. The entire Roman army, in wedge order, marched to victory. Suddenly the wings were attacked by the African battalions; the Gauls, the Iberians, [11] who had been in retreat, returned to the fight. The horsemen of Hasdrubal, in the rear, attacked the reserves. [12] Everywhere there was combat, unexpected, unforeseen. At the moment when they believed themselves conquerors, everywhere, in front, to the right, to the left, in the rear, the Roman soldiers heard the furious clamor of combat. [13]
The physical pressure was unimportant. The ranks that they were fighting had not half their own depth. The moral pressure was enormous. Uneasiness, then terror, took hold of them; the first ranks, fatigued or wounded, wanted to retreat; but the last ranks, frightened, withdrew, gave way and whirled into the interior of the wedge. Demoralized and not feeling themselves supported, the ranks engaged followed them, and the routed mass let itself be slaughtered. The weapons fell from their hands, says Polybius.
The analysis of Cannae is ended. Before passing to the recital of Pharsalus, we cannot resist the temptation, though the matter be a little foreign to the subject, to say a few words about the battles of Hannibal.
These battles have a particular character of stubbornness explained by the necessity for overcoming the Roman tenacity. It may be said that to Hannibal victory was not sufficient. He must destroy. Consequently he always tried to cut off all retreat for the enemy. He knew that with Rome, destruction was the only way of finishing the struggle.
He did not believe in the courage of despair in the masses; he believed in terror and he knew the value of surprise in inspiring it.