At daybreak of the 18th of June, Bülow, in conformity with the Order which he had received during the previous night from Blücher, quitted his position near Dion le Mont, to march through Wavre to St Lambert. This was the commencement of the important flank movement of the Prussians in support of the Anglo-Allied Army in position in front of Waterloo; and every measure of precaution was adopted with a view to its being carried into effect with certainty and safety. The sun had not yet risen when Major Witowsky was despatched with a Detachment of the 2nd Silesian Hussars, to Maransart, for the purpose of closely reconnoitring the Defiles of the Lasne, which had already been patrolled the evening before, and to observe the country in front of those Defiles, in the direction of the Enemy's position. Major Falkenhausen, previously mentioned as having pushed a reconnaissance beyond Seroulx on the 17th, was now directed also to reconnoitre the Lasne. Scouring parties were sent out, which kept up the communication that had been opened the previous day with Lieutenant Colonel Ledebur at Mont St Guibert: the whole country between the Dyle and the Charleroi high road was carefully explored; and correct intelligence was continually sent to the rear concerning the French Army.
By means of this vigilant look out, the Prussians secured the important advantage of retarding the communications between the French Emperor and his Marshal, since it compelled the bearer of despatches to pursue a very circuitous route.
At half past nine o'clock, on the morning of the 18th, whilst Bülow's Corps was on the march to St Lambert, the following additional despatch was forwarded to General Müffling:—
Wavre, 18th June 1815, at half past nine o'clock.
"I request you will say to the Duke of Wellington, in my name, that even ill as I am, I shall, nevertheless, put myself at the head of my troops, for the purpose of immediately attacking the Enemy's Right Flank, should Napoleon undertake anything against the Duke. If, however, the day should pass over without a hostile attack, it is my opinion that we ought tomorrow, with our combined forces, to attack the French Army. I commission you to communicate this as the result of my inward conviction, and to represent to him that I consider this proposal to be the best and most suitable in our present position.
"Blücher."
The Prussians very soon discovered that the French had made no disposition whatever for the protection of their Right Flank. Major Witowsky had proceeded as far as Maransart before he fell in with an Enemy's Patrol; and Major Falkenhausen found the Defiles of the Lasne perfectly free and unobserved. Upon receiving this intelligence, Blücher decided upon supporting the Anglo-Allied Army, by directing the march of his whole force, or at least of three Corps, towards the Wood of Paris, and debouching from thence upon the Flank and Rear of the Enemy; and Major Lützow was immediately despatched for the purpose of narrowly watching, from the other side of the above Wood, the French movements directed against the position of the Anglo-Allied Army.
No report as yet had been received from the Rear Guard, concerning Grouchy's advance, and as Blücher's object was now to gain the Defiles of the Lasne without interruption, and to occupy in force the Wood of Paris, he determined to avail himself of the time and opportunity which offered for the projected movement. Being, however, uncertain as to the amount of Grouchy's force, the Prince deemed it advisable that Wavre should not be abandoned until the greater part of the Army had passed the Defiles of St Lambert; and with this view, he directed that as soon as Bülow's Corps should have proceeded beyond Wavre, Zieten's Corps was to commence its march by Fromont and Ohain to join the Left Wing of Wellington's Army near La Haye. Pirch's Corps was ordered to follow Bülow's in the direction of St Lambert; and Thielemann's Corps, after retaining possession of the Defile of Wavre sufficiently long to render the general movement of the Army secure, was then gradually to follow Zieten's Corps upon Ohain.
An unfortunate incident occurred during the passage of Bülow's Corps, through Wavre, which materially impeded the march of the troops. The Advanced Guard, consisting of the Fifteenth Brigade (under General Losthin), with the 2nd Silesian Hussars, and a twelve pounder Battery, had scarcely passed through the town when a fire broke out in the main street, and extended itself with great rapidity. This not only caused a suspension of the march of the main body of the Corps, but created much alarm, in consequence of the great number of ammunition waggons in the place. Every exertion was made to extinguish the fire. The 1st Battalion of the 14th Regiment, under Major Löwenfeld, and the 7th Pioneer Company, were ordered upon this duty; and after they had encountered considerable difficulty, their efforts were crowned with success.
In the mean time the Advanced Guard of Bülow's Corps had continued its march, and reached St Lambert by eleven o'clock. The Sixteenth, and then the Thirteenth, Brigade arrived much later; and the Fourteenth Brigade, which formed the Rear Guard, was a long way behind. The Advanced Guard did not wait the arrival of the other Brigades, but proceeded forthwith to cross the Defile of St Lambert. Having effected the passage, which was attended with great difficulty, in consequence of the soft and miry state of the valley, it halted in the Wood of Paris, where it continued a considerable time, waiting for the approach of the main body. Patrols, however, from the 2nd Silesian Hussars, were immediately sent forward to feel for the Anglo-Allied Left, and to reconnoitre the French Right.
Zieten's Corps (the First) commenced its march, upon the left bank of the Dyle, towards Ohain, about noon.