On Thursday 15th June 1815, after his return from exile on the Island of Elba and the flight of the Bourbon King Louis XVIII, the Emperor Napoleon crossed the border from France into Belgium with his reconstituted French army and advanced north. The Duke of Wellington had his headquarters at Brussels with his army of British, German, Dutch and Belgian troops cantoned across the countryside. The Prussian army under Marshal Blücher lay to the East.
Napoleon expected Ney to occupy the Quatre Bras cross-roads during the afternoon of the 15th June 1815. For some unexplained reason Ney failed to do so. A squadron of Polish lancers from Ney’s Corps reconnoitred the cross-roads, finding it unoccupied, but withdrew. Soon after the departure of the lancers, one of Wellington‘s officers, the Prince of Saxe-Weimar, arrived at Quatre Bras with a small force of infantry and some guns. Recognising the importance of the cross-roads Saxe-Weimar remained there.
During the night of 15th June 1815, Napoleon formulated his plan of attack on the Prussian army which was rashly forming up around Ligny in Napoleon’s line of advance. Napoleon re-emphasised to Ney the importance of seizing the Quatre Bras cross-roads without delay the next day.
In the morning the French army began its attack on the Prussian positions around Ligny. If Ney complied with his orders he would take the cross-roads and then launch a devastating attack on the rear of the Prussian right wing at the point when Blücher’s men would be fully committed dealing with the heavy French frontal assaults.
In spite of his instructions, Ney failed to act with urgency and it was not until late morning that he began his move on the cross-roads. By this time a substantial number of allied units had arrived from the Brussels area. Ney found himself unable to make any headway against the troops holding Quatre Bras. The fighting continued for the rest of the day. At one point Ney launched a charge by a brigade of Kellerman’s cuirassiers. The British 69th, 30th and 33rd Regiments of Foot were swept aside in the assault, suffering significant casualties, but in turn the French cuirassiers, unsupported, were repelled and retreated in confusion taking much of Ney’s force with them.
Ney was unable to take Quatre Bras and his attack deprived Napoleon of a significant force that would have enabled him to defeat the Prussians conclusively, thereby preventing them from taking any part in the Battle of Waterloo the next day. In the event the intervention of Blücher’s army’s was one of the decisive factors in the Emperor’s final and conclusive defeat at Waterloo.