File:Prelude to the Battle of Waterloo

Description
Crossing the frontier near Charleroi before dawn on 15 June, the French rapidly overran Coalition outposts, securing Napoleon's favoured "central position" between Wellington's and Blücher's armies.

Only very late on the night of 15 June was Wellington certain that the Charleroi attack was the main French thrust. In the early hours of 16 June, at the Duchess of Richmond's ball in Brussels, he received a dispatch from the Prince of Orange, and was shocked by the speed of Napoleon's advance. He hastily ordered his army to concentrate on Quatre Bras, where the Prince of Orange, with the brigade of Prince Bernhard of Saxe-Weimar, was holding a tenuous position against the soldiers of Ney's left wing. Ney's orders were to secure the crossroads of Quatre Bras, so that, if necessary, he could later swing east and reinforce Napoleon.

Napoleon moved against the concentrated Prussian army first. On 16 June, with the reserve and the right wing of the army, he attacked and defeated Blücher's Prussians at the Battle of Ligny. The Prussian centre gave way under heavy French assaults, but the flanks held their ground. Ney, meanwhile, found the crossroads of Quatre Bras lightly held by the Prince of Orange, who successfully repelled Ney's initial attacks, but was gradually driven back by overwhelming numbers of French troops. First reinforcements and then Wellington himself arrived. He took command and drove Ney back, securing the crossroads by early evening, but too late to send help to the Prussians, who were defeated at the Battle of Ligny on the same day. The Prussian defeat made Wellington's position at Quatre Bras untenable, so the next day he withdrew northwards, to a defensive position he had personally reconnoitred the previous year—the low ridge of Mont St Jean, south of the village of Waterloo and the Forest of Soignes.

The Prussian retreat from Ligny went uninterrupted, and seemingly unnoticed, by the French. The bulk of their rearguard units held their positions until about midnight, and some elements did not move out until the following morning, completely ignored by the French. Crucially, the Prussians did not retreat to the east, along their own lines of communication. Instead, they too fell back northwards—parallel to Wellington's line of march, still within supporting distance, and in communication with him throughout. The Prussians rallied on Von Bülow's IV Corps, which had not been engaged at Ligny, and was in a strong position south of Wavre.

Napoleon, with the reserves, made a late start on 17 June and joined Ney at Quatre Bras at 13:00 to attack Wellington's army, but found the position empty. The French pursued Wellington, but the result was only a brief cavalry skirmish in Genappe just as torrential rain set in for the night. Before leaving Ligny, Napoleon ordered Grouchy, commander of the right wing, to follow up the retreating Prussians with 33,000 men. A late start, uncertainty about the direction the Prussians had taken, and the vagueness of the orders given to him meant that Grouchy was too late to prevent the Prussian army reaching Wavre, from where it could march to support Wellington. By the end of 17 June, Wellington's army had arrived at its position at Waterloo, with the main body of Napoleon's army following. Blücher's army was gathering in and around Wavre, around eight miles (13 km) to the east.

http://www.imdb.com/title/tt0066549/

http://en.wikipedia.org/wiki/Battle_of_waterloo#Prelude