Following defeat at the Battle of Ligny two days earlier, the Prussian army retreated north in some disorder, exposing the eastern flank of Wellington's Anglo-allied army at Quatre Bras, who also retreated northwards, to a defensive position at Waterloo. Napoleon moved the bulk of his army off in pursuit of Wellington, and sent Grouchy in pursuit of the retreating Prussians with the right wing (aile droite) of the Army of the North (L'Armée du Nord), a force consisting of 33,000 men and 80 guns.
The French units in the order of battle were:[a]
Grouchy was slow in taking up the pursuit after Ligny, which allowed Prince Blücher to fall back largely unmolested to Wavre, regroup his army, and then execute a flank march with three of his four corps to join up with Wellington's Anglo-allied army at Waterloo. The remaining corps, the III Prussian Corps (Thielmann's) of 17,000 men and 48 guns, was to follow the other three corps leaving a small rearguard in Wavre, unless the French appeared in force in which case he was to oppose any French attempt to close on the main body of the Prussian army.[a]