But if such good grounds exist for inferring that, on the 17th, an earlier and a clearer insight into the Enemy's movements might have been obtained by the Corps detached in pursuit of the Prussians, and that when obtained, it would have rendered the communication with the operations of the main Army on the left of the Dyle, a matter not only important in the highest degree, but also perfectly practicable; and if a failure in this respect be attributable to the absence of sufficient energy and vigour on the part of Grouchy, how much more forcibly does it not expose the extraordinary, the unaccountable, dilatoriness of Napoleon himself during the whole of the precious morning of the 17th! How striking a view it unfolds of what might have been accomplished, had the bivouac at Ligny been broken up a few hours earlier! Then, Wellington's Army was still between Quatre Bras and the narrow Defile of Genappe, open to an attack in front by Ney, simultaneously with one in flank by the force collected at Marbais (a part of which might have been detached across the Genappe, towards the rear of the Anglo-Allied Army, by Villers la Ville and Bousseval, masked by the Wood of Berme); and the rearmost Corps of the Prussian Army (Thielemann's), which was retreating through Gembloux, might have been attacked with effect, by the superior force of all Arms under Grouchy.
As regards Grouchy's movements during the early part of the 18th, it is very remarkable, that although he had in his despatch, written at ten o'clock the previous night, communicated to Napoleon his surmises of an intended junction of a portion of Blücher's forces with those of Wellington, and his consequent intention of following the Prussians in the direction of Wavre, afin qu'ils ne puissent pas gagner Bruxelles, et de les séparer de Wellington, and although he must or ought to have been aware that Wavre was only twelve miles distant from Napoleon's main line of operations, whereas Gembloux was about fifteen miles distant from Wavre, he not only delayed his departure from Gembloux until between seven and eight o'clock in the morning, but manœuvred by his right; taking the more circuitous line, through Sart à Wallain, and rendering his operations still more dilatory by moving both Vandamme's and Gerard's Corps along one and the same road. Had he not, from want of sufficient vigilance, continued ignorant of the fact, that the principal Prussian Column, consisting of the First and Second Corps, had retired upon Wavre, at so short a distance from his left as by the line of Tilly, Gentinnes, and Mont St Guibert, there can be very little doubt that he would have marched upon the latter point, which the Prussians, aware of its importance, had occupied with a Rear Guard; but even with the amount of information which he possessed, and with the inference justly impressed upon his mind that a co-operation between Blücher and Wellington was projected, we are at a loss to account for his not having moved upon Mont St Guibert, and manœuvred by his left.
In his despatch, written at two o'clock in the morning, he mentioned to the Emperor his design of marching upon Corbaix or Wavre; a movement of which Napoleon, in his reply, expressed his approval; and if he had directed one of his Infantry Corps along the line of Corbaix and La Baraque, and the other by that of Mont St Guibert and Moustier, there can be no doubt that, even late as was the hour at which he started from Gembloux, he would, in a great measure, have fulfilled the expectations of his Imperial Master. In this case, he would naturally have so divided his Cavalry, that one portion would have scoured the country along the Front and Right of the Column marching by Corbaix and La Baraque, and the other portion would have been employed in a similar manner along the Front and Left of the Column moving upon Mont St Guibert and Moustier. Both at this point and at Ottignies, about eight hundred yards lower down the stream, there is a stone bridge across the Dyle. There is a direct road from Moustier to St Lambert, scarcely five miles distant, and another to the Field of Waterloo. The Cavalry in advance of the Left Column could not have failed to discover the Prussian troops in march to join the Left of Wellington; for they were then passing slowly, and with extreme difficulty, through the Defiles of St Lambert and Lasne. This discovery would have led to the Right Column being moved by its left, from La Baraque to Moustier; the Cavalry attached to it masking the movement as long as possible. The Left Column would then, in all probability, have followed its advanced Cavalry to St Lambert; and the Right Corps have either moved upon the same point as a reinforcement, or have diverged upon Lasne as a Support, upon which the former might have fallen back, if compelled to effect its retreat towards Planchenoit.
In this manner might Grouchy have so far realised the anxious expectation of Napoleon as to have fallen upon Bülow flagrante delicto, and have materially procrastinated the co-operation of Blücher with Wellington on the 18th of June; a co-operation which a contrary proceeding, originating in fatal tardiness of movement, and exhibiting useless manœuvring in a false direction, could not fail to render easy in execution and successful in result. But beyond such procrastination of the meditated junction of Blücher's and Wellington's forces, Grouchy could have effected nothing. The junction itself could not have been prevented. The tendency of Grouchy's movements had been too narrowly watched; the country between the Dyle and the Charleroi road to Brussels had been too vigilantly explored; and the movements, in succession, of the different Prussian Corps had been too nicely calculated and determined; to admit of the possibility of a failure, as regarded the arrival of a considerable portion of the Prussian forces on the Left of the Anglo-Allied Army.
Blücher had made so admirable a disposition of his four Corps d'Armée, that two of them could at any time have combined, and therefore have presented a superior force to Grouchy, at any point between Wavre and Planchenoit; whilst the remainder of the Army might have continued its march to the Field of Waterloo. Had Grouchy moved by St Guibert and Moustier upon St Lambert, Thielemann's Corps would then have been on the march towards Couture, according to his original instructions; and finding Bülow engaged with the Enemy, would have joined him. Grouchy might then have contrived to hold both these Corps at bay, and thus have reduced the co-operating Prussian force at Waterloo to the two Corps under Zieten and Pirch, besides considerably retarding that co-operation; since without having experienced the effects of any such interruption to the progress of the other Corps, as we have here supposed, these two Generals did not reach the Field of Battle until seven o'clock in the evening of the 18th.
Such is the extent of the advantage which, under the circumstances, Grouchy would have gained by a march from Gembloux upon St Lambert; a most important one, no doubt, as time for pushing the struggle with Wellington, with the whole force at his immediate disposal, before the arrival of the Prussians, was of the most vital consequence to Napoleon; and this advantage Grouchy entirely lost by his march upon Wavre—a march which enabled Blücher to appear with three, out of his four, Corps d'Armée, on the great and decisive Field of Action; and that in sufficient time to render the victory as complete as could reasonably be desired.
No exertions, however, on the part of Grouchy, after he broke up from Gembloux on the morning of the 18th, could have effectually frustrated the junction of Wellington and Blücher. Two great errors, for which that Marshal was not accountable, reduced the contemplated junction from a measure of calculation to one of certainty. The first and principal of these has already been adverted to at some length, and cannot be too closely kept in view—the fatal neglect of a vigorous pursuit of the defeated Prussians, on the night of the 16th and morning of the 17th, by a detached Corps; combined with the extraordinary delay in the attack upon Wellington at Quatre Bras, on the latter day. The second error arose from the want of a strong reconnaissance and vigilant look out on the right of the main French Army, on the morning of the 18th, followed up by the occupation of the Defiles of the Lasne.
It was nearly four o'clock when Vandamme's Corps arrived in front of the position which Thielemann was in the act of quitting, with a view to follow and support the remaining three Prussian Corps that were at that moment on the march towards the Field of Waterloo; and, with a fire that was opened from the French Batteries, commenced the Battle of Wavre, which will be described in its proper place in a subsequent Chapter.