Before resuming his story, Hugo acquaints the reader with such peripheral matters as the topography of Waterloo, a description of the farm of Hougomont, where Napoleon encountered his first setback, certain military considerations, and the emperor's personality.
Only then does the author launch into the long chronological narration of the Battle of Waterloo. It is the morning of June 18, 1815. In spite of the rain of the previous night which interferes with his plans, Napoleon exudes confidence. The army is in position, his strategy is decided. He gives the order to attack, expecting to deliver his usual stunning blow, but the British prove to be unusually stubborn opponents, and Napoleon suffers staggering losses in forcing Wellington to retreat on the Mont Saint Jean plateau.
The emperor orders Milhaud's cuirassiers, a formidable regiment 3,000 strong, to crush the enemy. Headed by Marshal Ney, they gallop like a massive juggernaut toward the British forces, but fate intervenes, putting in their path a sunken road impossible to detect from a distance. The troops fall headlong into it, carried on by their own impetus. Men and horses serve as a living bridge for their comrades to cross. The British assemble their artillery and proceed to shell the survivors.
The remainder of the regiment, however, continues the charge and hurls itself furiously on the enemy; in spite of the deadly calm efficiency of the British infantry, the regiment slices deep gaps in the British formations. Wellington orders his cavalry to attack from the rear, and suddenly the assailant becomes the defender, and the charge becomes a general slaughter. In one minute the cuirassiers lose 600 men, and the British formations are reduced from thirteen to seven.
Both sides are seriously weakened, but Wellington's losses are the greatest. His cavalry is destroyed, his artillery largely disabled, and panic begins to infect his ranks. At five o'clock, he is forced to the somber admission, "Blucher [that is, reinforcement by the Prussian army that was supposed to join him earlier in the day] or the night."
Miraculously, a few minutes later, a line of bayonets sparkles on the horizon. Blucher's army, held up by the rains of the previous day, has arrived. This new intervention turns the tide of battle. Caught between Prussian shells and the bullets of the reinvigorated British, the French offensive turns into a rout, into disaster, into extermination.
Still the French do not succumb. Napoleon sends his picked troops, the Imperial Guard, against the British; marching resolutely against the enemy in the tide of universal retreat, it is mowed down rank by rank. Ultimately the whole Guard is destroyed: "Not one man misses his appointment with suicide." After this, panic is complete, and the French army turns into a disorganized mob that sweeps over the countryside pursued by Blucher's troops, who give no quarter.
One incident remains to be told, unimportant to the course of history, but illustrative of man's undying spirit. At the end of the battle, an obscure officer named Cambronne is one of the few men still resisting. To the British exhortations to surrender, he answers with one eloquently obscene word.
After the French defeat, the field is abandoned to the scavengers. Among the most industrious we find a certain Thénardier, who methodically proceeds to strip the dead. Suddenly a hand grabs him from behind. It is a dying officer clutching him for help. Calmly Thénardier removes him from the cadavers and pockets his valuables. The officer, a man called Pontmercy, ironically believes Thénardier has saved his life and, asking his name, says he will never forget him.
For some critics, this description of the Battle of Waterloo is simply a typical example of nineteenth-century long-windedness, but in fact it is a vital part of Les Misérables. The society that persecutes Jean Valjean is not irrevocably cruel; it is capable of change and of radical change in the interest of the poor and oppressed, as the Revolution showed. Napoleon I, dictator though he was, was a child of that Revolution and consolidated some of its liberal social advances. With his defeat at Waterloo and the consequent restoration of the Bourbons, social progress was checked; Jean Valjean, Fantine, Cosette, and thousands of others like them were again neglected. But their fate is not inevitable; history may again intervene to reverse the effects of Waterloo, and it is one of Hugo's purposes in writing Les Misérables to encourage it to do so.
Furthermore, Hugo uses the battle scene to warn us that his stage and his cast of characters is about to widen and that we shall meet not only characters from Book I, like Thénardier, but others yet unknown to us, of whom Pontmercy is the forerunner.
Finally, the epic quality of this book underlines the epic quality of the novel as a whole. The same capricious fate thwarts indifferently the plans of Napoleon I and M. Madeleine; the men of Waterloo and Jean Valjean struggle against their destinies with the same blind determination and terrible valor. From the moment when Hugo leads us, unsuspecting, through the gate of the farm of Hougomont with its brave bird singing and its banks of violets, we are in the hands of a great poet, who is as sensitive to the nuances of war as to those of everyday life and sees in both alike pity and horror, irony and beauty.