Two days earlier, at Ligny, the French had given the retreating Prussians no mercy. Now the Prussians returned the favor. The cavalry that streamed south from the Waterloo battlefield was not interested in prisoners. At Genappe, Marshal Lobau scraped together three hundred men and tried to make a stand at the bridge over the river Dyle - the only crossing in the defile. The Prussians scattered them and captured Lobau himself within minutes. A Prussian officer reported eight hundred Frenchmen lying dead in the streets of the small town. The Brunswick cavalry, whose Black Brunswickers had lost their duke at Quatre Bras two days before, asked permission to join the pursuit. They got it. One Brunswick hussar, recognizing General Duhesme of the Young Guard at a Genappe inn, refused his request for quarter and cut him down. The Duke fell the day before yesterday, the hussar said, and thou also shalt bite the dust. Other accounts say Duhesme was already mortally wounded from the battlefield and died in Prussian medical care that night. The two versions tell you something about how the legend grew.

Napoleon reached Charleroi at daybreak on 19 June. He had perhaps an hour to catch his breath before Prussian cavalry forced him across the Sambre. He stopped briefly at Philippeville to send orders to scattered corps commanders - General Rapp, General Lecourbe, General Lamarque - telling them to march by forced marches on Paris. He told Marshal Soult to gather the remnants at Laon. Then he took post horses and rode for the capital. A pamphleteer of the time inscribed an old line about the rebel Catiline over the Charleroi gate: Abiit. Excessit. Evasit. Erupit. - He has left, absconded, escaped, disappeared. The military historian William Siborne thought it was the perfect epitaph for the Emperor's flight.

Forty kilometers to the east, Marshal Grouchy commanded thirty thousand French troops who had no idea the main army was destroyed. They had been fighting their own battle at Wavre against the Prussian III Corps. Around 11:00 on 19 June the news finally reached Grouchy that Napoleon's army was scattered across the Belgian frontier. He briefly considered marching on the Prussian rear - he was perfectly positioned to do real damage - then decided he was outnumbered and turned south for Namur instead. His retreat through the upper Meuse defile was textbook. He used cavalry feints to keep Thielmann's Prussians at Wavre well after he had already gone. He left General Teste's division to hold Namur as a sacrifice rearguard. On 20 June, Teste's men barricaded the gates of Namur and fought the Prussian II Corps street-by-street, losing 1,500 men but buying the rest of Grouchy's wing enough time to escape down the river to Dinant. Pirch's Prussian II Corps lost 44 officers and 1,274 other ranks taking the Porte de Fer. Grouchy's textbook withdrawal probably saved a third of Napoleon's army from immediate destruction.

Wellington and Blucher operated very differently on the march south. The Duke's Anglo-allied army crossed the French frontier on 21 June and Wellington made his headquarters at Malplaquet - the site of Marlborough's 1709 victory, a place he chose deliberately. From there he issued a proclamation that became the campaign's signature document: his army came as liberators against the usurper Napoleon Bonaparte, not as conquerors of France. Soldiers who looted would be punished. Civilians who did not resist would be respected. Wellington thought a brutalized France would never accept the restored Louis XVIII, and would make another war inevitable. The Prussians, who had spent two decades being trampled by French armies, took a different view. Their march was marked by what contemporary observers politely called severe exactions. The British and Germans under Wellington inspired confidence; the Prussians, one chronicler wrote, awed the locals into subjection. Both armies got where they were going. They just left very different memories behind.

On 23 June, with both armies halted to let stragglers catch up, the two commanders met at Catillon-sur-Sambre to plan the final approach to Paris. They knew the French were collecting their forces at Laon and Soissons, directly on the road. So they decided to swing west - cross the Oise at Compiegne or Pont-Sainte-Maxence, turn the French left, and either trap the retreating army or reach the capital first. To keep the French guessing, Prussian cavalry would follow the original road, hoping the French would mistake it for the main advance. The plan worked. By 24 June Zieten's Prussian I Corps had taken the fortress of Guise without firing a single cannon shot. The British 4th Division stormed Cambrai that evening, losing eight killed and twenty-nine wounded. French envoys appeared at Brunswick and Prussian outposts proposing a suspension of hostilities - Napoleon had abdicated in favor of his son, they said, a Provisional Government had been formed. Wellington and Blucher refused. The next week they would be in Paris. The week after that, on 8 July, Louis XVIII would be back on the throne, and the Hundred Days would be over. Five hundred kilometers of dust and exhaustion and drumbeats in the dark had remade Europe.