Thielemann intended that the Ninth Brigade should be posted in rear of this general disposition of his troops, so that its services might be made available according as circumstances might require; but through some misunderstanding in the transmission of the Order, General Borcke was induced, after having moved along the Brussels road until near La Bavette, thence to turn off to his left, and continue his march, according to his original instructions, in the direction of Fromont, Bourgeois, and St Lambert, towards Couture; being under the impression that the whole Corps had already commenced this march, in pursuance of the general plan, and that his Brigade was destined to cover the movement. The departure of the Brigade was not immediately discovered; and thus, by this misunderstanding, Thielemann's force suffered an unexpected reduction of six Battalions and the Foot Battery No. 18; and consisted, therefore, of only 15,200 men; with which number he had now to contend against Marshal Grouchy's force, amounting altogether to 33,765 men.
Thielemann's position was certainly a very favourable one, and the occupation of it was arranged with great skill. As it was impossible to foresee in what manner the attack upon it would be conducted; whether it would be directed against one particular Bridge, or against all the Bridges, with the design of carrying the whole Line by storm: Thielemann limited the occupation of the town and of the line of the river to the number of Light Troops which might be sufficient for sustaining any sudden assault; taking care to have Supports close at hand for that purpose: but disposing his Reserves, which comprised his main force, so that they might become available at any point which might be pressed; or, should the Enemy develop greatly superior numbers, as was subsequently the case, serve to guard against any flank attack.
As before explained, it was Vandamme's Corps which arrived in front of Wavre between three and four o'clock. Two Batteries, of which one consisted of twelve pounders, were drawn up on the right of the road overlooking the valley, and opened the cannonade. These were subsequently reinforced by a third Battery, posted on the left of the road. Excelmans' Cavalry Corps was posted in right rear of Vandamme. Gérard, with the Fourth French Corps, was still in the rear on the march; and Pajol, with his Light Cavalry, had only just passed through Tourrines, situated scarcely half way between Gembloux and Wavre. Marshal Grouchy sent word to both these Officers to accelerate their march.
Whilst the French Skirmishers were gradually forcing back the Prussian Light Troops into the valley, Grouchy, hearing a powerful cannonade in the distance to his left, rode off a little way in that direction; and concluding that Napoleon was closely engaged with Wellington, conceived that as he had now reached the Prussians, he would best fulfil his instructions by vigorously attacking them, so as to prevent their detaching reinforcements to the Anglo-Allied Army. He was quite ignorant as to the strength of the Enemy in his front, and was in doubt whether the whole Prussian Army was before him, or merely a strong Detachment. Of the fact that three Prussian Corps were on the march to co-operate with Wellington's forces, he of course knew nothing. In this state of uncertainty, and with his troops aux prises with the Prussians, he was fearful of detaching to his left; since by so doing, he would expose himself to the risk of his main force becoming overpowered by superior numbers, and his Detachment cut off.
Independently of other considerations which might have assisted in dissuading Grouchy from detaching a portion of his force at this period, such as the length of time his troops had been upon the march, along bad and miry roads; he was perfectly justified, under all the circumstances of his then position, in adopting this course of proceeding. And even if he had been fully cognisant of the actual disposition of the Prussian Army, he could at this time have rendered no essential service to Napoleon; the opportunity for doing so had been suffered to pass by, as was fully explained in Chapter VIII.
His total ignorance, however, of Blücher's proceedings, and of all that was then taking place between Wavre and the Field of Waterloo, afforded undeniable proof of his having completely failed in acting up to the spirit of the instructions he had received, not to lose sight of the Prussians, and in exercising that degree of enterprise, energy, and decision, which Napoleon had so naturally anticipated from a General of Grouchy's note and experience; especially when entrusted with so important a command, under such highly critical circumstances.
A message having reached Grouchy from Pajol, communicating his having fallen into the Marshal's line of operation, he directed that General to move upon Limale. His Right Flank, however, continued to be protected by the 17th Dragoons, detached from General Berton's Cavalry Brigade (of Excelmans' Corps) en reconnaissance, towards the high road leading from Namur to Louvain.
In the mean time, a vigorous cannonade was maintained between Vandamme's and the Prussian Batteries across that part of the valley in which lay the town of Wavre. Under cover of the French guns, the Skirmishers pressed down upon that portion of the town situated upon the right bank of the river, and of which they soon gained possession; the Prussians having previously decided upon not making any effort to retain it. On reaching the river, however, they were met by a most destructive fire of musketry from the opposite houses and the Bridge. The contest now became desperate, and the defence of the Dyle was obstinately maintained by the Prussians. The Skirmishers rapidly extended on either Flank along both banks of the river from Bierge as far as Bas Wavre. All the Prussian Brigades pushed forward their Sharpshooters. Those of the 4th Kurmark Landwehr took up the Line between the Town and Bas Wavre, those of the 3rd Kurmark Landwehr took post in the Town, between the two Bridges; on the right of the latter stood the Sharpshooters of the Tenth Brigade; and those of the Twelfth Brigade formed the Right Wing of the whole Line at Bierge.
This tiraillade had continued about an hour, when General Hulot's Division of Gérard's Corps d'Armée reached the Field; and received Orders to take possession of the Mill at Bierge, and to cross the Dyle at that point. A Battalion of Vandamme's Corps was at the time vainly attempting to effect a passage. Upon the Height opposite Bierge were several guns of the Third Corps, endeavouring to keep down the fire from the Prussian Batteries on the other side of the valley.