In this state of uncertainty and suspense, the Emperor sent for General Domon, and desired him to proceed instantly with a strong reconnoitring party to the right, and procure correct intelligence; to put himself quickly in communication with the troops approaching from St Lambert; to effect a junction with them, if they belonged to Marshal Grouchy, and to impede their advance if they proved to be Enemies. At the same time, the two Light Cavalry Divisions of Domon and Subervie proceeded some distance in the direction of the Wood of Paris; and were then drawn up en potence to the Right of the French Army.

Not long after Domon's departure, Napoleon's impatience to ascertain the precise character of the distant Column was relieved by the arrival of an Officer of Chasseurs with a Prussian Hussar, who had just been taken prisoner; and who was the bearer of a letter, addressed by the Prussian General Bülow to the Duke of Wellington, to acquaint the latter with his arrival at St Lambert. The prisoner stated that the Column which was perceptible in the vicinity of this Village, was the Advanced Guard of Bülow's Corps, which had not been engaged at Ligny; that he had been in the morning at Wavre; that the three other Prussian Corps were stationed close to that town, and had passed the previous night there, without perceiving any indication of an Enemy in their front; and that a Patrol of his own Regiment had advanced, during the night, as far as two leagues from Wavre without encountering any body of French troops.

Soult who had just at that moment written the following letter to Grouchy, in reply to his Second Report from Gembloux, immediately added a postscript, referring to the above intelligence, and sent off the despatch, accompanied by the intercepted communication and the Hussar's report.

"Du champ de Bataille
de Waterloo, le 18, à
une heure après midi. 		"On the Field of Battle
at Waterloo, the 18th, at
one o'clock in the afternoon.
"Monsieur le Maréchal, "Monsieur Marshal,
"Vous avez écrit ce matin, à deux heures, à l'Empereur que vous marcheriez sur Sart à Wallain; donc votre projet était de vous porter à Corbaix ou à Wavres: ce mouvement est conforme aux dispositions qui vous ont été communiquées: cependant l'Empereur m'ordonne de vous dire que vous devez toujours manœuvrer dans notre direction; c'est à vous à voir le point où nous sommes pour vous régler en conséquence et pour lier nos communications, ainsi que pour être toujours en mesure pour tomber sur quelques troupes Ennemies qui chercheraient à inquiéter notre Droite, et les écraser. En ce moment la bataille est engagée sur la ligna de Waterloo. Le Centre de l'Armée Anglaise est à Mont Saint Jean, ainsi manœuvrez pour joindre notre Droite. "You wrote at two o'clock this morning to the Emperor that you would march on Sart à Wallain; consequently your plan was to proceed to Corbaix or to Wavre. This movement is in accordance with the dispositions which have been communicated to you: however the Emperor orders me to say to you that you ought always to manœuvre in our direction. It is for you to consider our present position in order to guide yourself accordingly, and to knit up our communications in such a way as to be always within limits to fall upon some of the Enemy's troops which would endeavour to annoy our Right, and to crush them. At this moment the Battle has commenced on the line of Waterloo. The Centre of the English Army is at Mont St Jean, so manœuvre to join our Right.
"Le Duc de Dalmatie. "The Duke of Dalmatia.
"P.S.—Une lettre qu'on vient d'intercepter porte que le Général Bülow doit attaquer notre Flanc. Nous croyons apercevoir ce Corps sur les Hauteurs de Saint Lambert; ainsi ne perdez pas un instant pour vous rapprocher de nous et nous joindre, et pour écraser Bülow que vous prendrez en flagrant délit." "P.S.—A letter which has just been intercepted states that General Bülow is about to attack our Flank. We believe we see this Corps on the Heights of Saint Lambert; therefore lose not an instant in coming nearer to us and joining us, and in crushing Bülow whom you will take in the very act."

The above letter is of much historical importance. Although conveying Napoleon's approval of Grouchy's movement upon either Corbaix or Wavre, it clearly indicates the commencement of that anxiety and uneasiness of mind which the Emperor experienced through the fear of even the possibility of a want of just conception on the part of the Marshal, of the true spirit in which the combination of his movements with those of the main Army should be carried on. He draws the Marshal's attention to the necessity of his manœuvring so as to prevent the execution of any hostile design against the Right Flank of the main Army, which is then engaged with Wellington's forces, and names Mont St Jean, the Centre of the Duke's position, as a guiding point. This anxiety was naturally augmented very considerably by the discovery of Bülow's troops, and the postscript accordingly enjoins still more urgently the necessity of a close and active co-operation.

Very shortly after the Officer who was the bearer of this despatch had started, a message was sent in by General Domon to the effect that his Scouts had fallen in with Detachments from the Enemy in the direction of St Lambert; and that he had just sent out Patrols towards other points to obtain intelligence of Marshal Grouchy, and to communicate with him, if practicable.

It is to be observed, however, that the troops discovered by the French Cavalry did not belong to Bülow's main body, but merely to his Advanced Guard. The former was the mass first seen from La Belle Alliance, when it was moving across the Heights of St Lambert, on the right or opposite bank of the Lasne; but as explained in a preceding Chapter, it encountered great obstruction and much delay during its march towards the Field: whilst the latter, awaiting its arrival, rested concealed in the Wood of Paris, near Lasne.

Thus it appears that both Commanders were deceived as to the proximity of any considerable body of Prussians at this period of the day. Nevertheless, the conviction of such a proximity, while it imparted increased confidence to Wellington, in regard to the speedy execution of the plan of combined operation which he had preconcerted with Blücher, compelled Napoleon to employ additional vigilance and circumspection upon his Right Flank.

Great, however, as was the necessity for such vigilance; the measures that were adopted were lamentably deficient in energy, vigour, and judgement. Considering that the main body of Bülow's Corps was on the point of entering the Defile of St Lambert, in which it had to overcome the greatest difficulties; it appears unaccountable that the Officer employed in reconnoitring and patroling beyond the extreme Right of the French Army should not have urged the occupation of the Wood of Paris with a detached body of Infantry, with a view to impede Bülow's advance, and compel him to take a more circuitous route. In this manner the Prussian co-operation might have been so far obstructed or delayed as to secure to Napoleon the power of advancing against Wellington with almost the entire of his force; and of thus, perhaps, accomplishing his grand object of defeating both Armies in detail.

No disposition of this kind was made; but, in place of it, Domon's and Subervie's Light Cavalry Divisions were moved to the right, en potence to the Front Line, their Picquets not extending beyond the plateau in front of the Wood of Paris. Whether this culpable neglect arose from the want of due penetration and foresight on the part of General Domon; or from this Officer having been instructed not to act as if in command of a detached Corps, but only to take up a position, within a prescribed distance, en potence to the general Front Line; or, from an over confident expectation on the part of Napoleon of approaching aid from Grouchy; are points not easily determined: but there can be no doubt that the error of not occupying the Wood of Paris with a strong body of Infantry, flanked and supported by the Cavalry, was fatal to the development of Napoleon's original design. One Infantry Division, combined with Domon's and Subervie's Cavalry Divisions, would have sufficed for obstructing the debouching of Bülow's Corps from the almost impassable Defile of St Lambert; and compelling it to move by its right, into the line of march of Zieten's Corps, which did not reach the field before seven o'clock in the evening. To move by its left, along the deep and miry valley of the Lasne, would have been impracticable so long as the Wood of Paris and its vicinity continued to be occupied by the French.