On the evening of the battle of Ligny, Napoleon marches towards Waterloo. Victorious over the Prussians, the Emperor joined Marshal Ney, who failed to beat the British, Belgian and Dutch allies at the Battle of Quatre-Bras. The emperor left Marshal Grouchy to hunt down what he believes to be a routed Prussian army. While the cannon thundered at Waterloo, Grouchy's army corps engaged the Prussians in the Battle of Wavre. Did Grouchy make a mistake in not marching to the sound of the cannon towards Waterloo? Did he just follow the Emperor's order? This volume devoted to a completely unknown Napoleonic battle attempts to restore the truth about this episode. After the study of the Battle of Wavre, this work presents for the first time in a comprehensive way the battles of Namur and the exemplary retreat of the French army to France, zealously organized by Grouchy. This volume closes the trilogy of battles that precede the final confrontation at Waterloo.