The bivouac on the battle field of Quatre Bras, during the night of 16 June, continued undisturbed until about an hour before daylight, when a cavalry patrol having accidentally got between the adverse pickets near Piermont, caused an alarm in that quarter that was quickly communicated to both armies by a rattling fire of musketry, which, rapidly augmenting, extended itself along the line of the advanced posts.

[5][b] Captain Grey directed Lieutenant Bacon to patrol towards the house, while he remained with the remainder of the troop, concealed from the French, a disposition favoured by the nature of the ground, and the trees in the hedges, on both sides of the road.

On this position he might rely upon the aid of a sufficient portion of Blücher's forces from Wavre which combined with his own would enable the Coalition to confront Napoleon and his main army with a numerical superiority at a decisive point.

In the early part of the morning, Marshal Ney had, like his opponent, been ignorant of the result of the Battle of Ligny; but he was aware that the Anglo-allied army had been considerably reinforced during the night, principally by the arrival of its cavalry.

[19] In this uncertainty, Ney sent a message by General Count Flahaut, who happened to be still with him, and who was returning to rejoin Napoleon wherever he might be found, expressive of his anxiety to learn the result of the action of the preceding day.

The military historian William Siborne states that while Ney was thus justified in remaining inactive during the early part of the day, the fact of Napoleon's not moving directly upon Genappe with the morning's dawn, and his excessive delay in breaking up his bivouac at Ligny, are inexplicable.

A glorious opportunity had presented itself for the attainment of his original design of defeating both Armies in detail, but which was completely lost by a most extraordinary and fatal want of energy and vigour in seizing upon the advantages which the victory of Ligny had placed within his reach.

[22] The Anglo-allied infantry having, some time previously, entirely crossed the Dyle,[d] with the exception of the light companies of the 2nd Brigade of Guards (Byng's) on the right, and of the 1st Battalion 95th Rifles, on the left, which troops had been directed to remain until the last moment, and were now retiring to Genappe (where they were subsequently drawn up at the entrance of the town).

The 5th's remaining regiment, the 2nd Hussars of the King's German Legion (Linsingen's), was manning a line of observation posts on the French frontier, extending from Kortrijk (Courtrai), through Menen (Menin), Ypres, Lo (Loo), and Veurne (Furnes) to the North Sea.

[26] These dispositions had scarcely been arranged, when the picket of the 18th Hussars, on the left, came in at a good round trot, followed by two or three squadrons of French cavalry, upon which Vivian's Battery of Horse Artillery (Frazer's), opened a fire whereby their advance was checked.

The good countenance here shown by Vivian's Brigade, combined with the soft and miry state of the ground after the thunderstorm had set in, completely checked the pursuit by the French cavalry, which now turned towards the high road.

[37] The Right Cavalry Column, consisting only, as previously stated, of the 1st and 2nd Light Dragoons of the King's German Legion, and of the British 15th Hussars, effected its retreat in good order, protected by its skirmishers, as far as the ford, which it crossed above Genappe.

Upon the arrival of the Squadron at the opposite entrance of Genappe, it was posted between this point and the main body of the 7th Hussars, which had been drawn up on the road in a column of divisions, prepared to check the advance of the French on their debouching from the town.

[37] Lieutenant General the Earl of Uxbridge, the commander of the British cavalry, wanted to check the French advance and gain sufficient time for the orderly retreat of the Anglo-allied army as well as to prevent a compromise of any portion of the rearmost troops.

In a few moments afterwards, the French column showed its head within the town; the leading troop consisted of lancers, all very young men, mounted on very small horses, and commanded by a fine looking, and, as it subsequently transpired, a very brave man.

[44] The latter, animated by the presence of the commander of the cavalry, who was also their own Colonel, rushed forward with the most determined spirit and intrepidity; while the French, awaiting the onslaught, opposed to them a close, compact, and impenetrable phalanx of lances; which, being securely flanked by the houses, and backed by a solid mass of horsemen, presented a complete chevaux de frise.

[47] During this contest, the French, having become sensible of the evil that might arise from the closely wedged state of the cavalry in the town, began to clear the rear of the most advanced portions of the column, so as to admit of more freedom of movement in case of disaster.

[47] So exceedingly elated were the French with having repulsed the 7th Hussars in this their first serious encounter with the British cavalry, that immediately on that Regiment retiring, the whole column that was in Genappe raised the war cry, and rent the air with shouts of "En avent!

[47] evincing the greatest impatience to follow up this momentary advantage, and to attack the supports; for which, indeed, the opportunity appeared very favourable, as the ranks of the latter were suffering considerable annoyance from the well directed and effective fire of the French guns on the opposite bank of the river.

[47] Uxbridge, seizing upon the advantage presented for attacking the French cavalry while moving up hill, with their flanks unsupported, and a narrow defile of the town and its bridge in their rear, brought forward 1st Life Guards through the 23rd Light Dragoons, who opened out for their passage to the front.

The Life Guards now made their charge, most gallantly headed by Colonel Sir John Elley, Deputy Adjutant General, who, at the moment of contact with the French, began by cutting down two men right and left.

He kept the light cavalry, protected by the Household Brigade, as the rearguard, and slowly retired into the chosen position in front of Waterloo, the guns and rockets constantly plying on the French advanced guard, which, although it pressed forward twice or thrice, and made preparations to attack, never ventured to come to close quarters with its opponents; and the column received from it no further molestation.

It was by means of this reconnaissance that Napoleon ascertained the retreat, through Tilly and Gentinnes, of the principal Prussian column, consisting of I and II Corps (Zieten's and Pirch's), although the line by which they retired was undiscovered by Grouchy (on 17 June), in whose immediate sphere of operations it was situated.

[54] This mass of French infantry suffered severely from the fire, to which it stood exposed about half an hour; for the head of the column having been unable to retreat, in consequence of the pressure from its rear, and prevented by the high bank on either side of the road from filing off to a flank, could not readily extricate itself from so embarrassing a situation.

Pickets were hastily thrown forward by both armies, and to so great a height had the mutual spirit of defiance arisen, that the near approach of opposing parties, advancing to take up their ground for the night, led to little cavalry skirmishes, which, though unproductive of any useful result to either side, were distinguished, on different points of the lines, by a chivalrous bravery which seemed to require a prudent restraint.

A very spirited charge was also made by the right troop of the 2nd Light Dragoons of the King's German Legion, under Lieutenant Hugo; who was allowed by his commanding officer to volunteer for that service, and who, from the vicinity of Hougomont, boldly rushed up the Height intervening between that point and Mon Plaisir, and drove back a portion of the French advanced guard of cavalry; recapturing at the same time three carriages filled with British sick and wounded.

[56] Wellington who had, from the commencement of the campaign, considered it very possible that Napoleon would advance by the Mons road, still entertained apprehensions of an attempt on the part of his opponent to turn him by Hal, and seize Brussels by a coup de main.

[59] In the opinion of the military historian William Siborne writing in the decades after the events, the manner in which Wellington withdrew his army from the position of Quatre Bras to the one of Waterloo, must ever render that retreat a perfect model of operations of this nature, performed in the immediate presence of a powerful enemy.

Those dispositions which have been described as having been made by him for the purpose of masking the retirement of the main body, of affording perfect security to the passage of the defile of Genappe in his rear, and of ensuring the orderly and regular assembly of the several corps on the ground respectively allotted to them in the new position, evince altogether a degree of skill which had never been surpassed.

[62] Archibald Frank Beck the author of the Encyclopedia Britannica Eleventh Edition article on the campaign states that with the defeat of the Prussians Napoleon still had the initiative, for Ney's failure to take the Quatre Bras cross roads had actually placed the Anglo-allied army in a precarious position.