BLÜCHER had quitted Wavre before eleven o'clock in the forenoon, and repaired to the vicinity of Limale, in order to make himself acquainted with the nature of the country in the direction of St Lambert. Whilst here, he received intelligence of the approach of the Enemy towards Wavre. Colonel CLAUSEWITZ, Chief of the Staff of the Third Corps, was immediately made the bearer of an Order for THIELEMANN to defend the position at this place, in the event of the Enemy advancing in force; but, should the latter cross the Dyle higher up the stream, or not appear in great strength (a point concerning which nothing positive was then known), he was to leave only a few Battalions in position at Wavre, and to follow the main Army, with his Corps, as a Reserve, in the direction of Couture.
GROUCHY's movements, on the 17th and 18th, form so striking a feature in the history of this Campaign, and exercised so important an influence upon the fate of the decisive Battle of Waterloo, that it becomes an essential point in the study of that history, to examine how far he complied with, and carried into effect, the instructions received from his Master, and to what degree his proceedings, consequent upon his ascertaining the direction of the Prussian retreat, coincided with the general plan and object of NAPOLEON's operations. On a reference to the account of his transactions during the 17th, given in the despatch written at ten o'clock on that night, it appears he was completely ignorant of the line by which the principal mass of the Prussian Army had retreated, namely, that of Tilly and Gentinnes, by ZIETEN's and PIRCH's Corps, although his Cavalry had driven back the Prussian Detachment from the latter place to Mont St Guibert, but from whence it appears to have been withdrawn in the night. His attention seems to have been much less devoted to this quarter than it was to his Right, in which direction he detached as far as Perwès. The main body of his forces did not proceed further than Gembloux on the 17th, that is, about five miles from the Field of Ligny.
Upon a first consideration, we are strongly impressed by the striking contrast between this march, in pursuit of a defeated Army, which had commenced its retreat on the previous night, and which presented no check to the advance, and the march of NAPOLEON from the same Field, by Quatre Bras and Genappe, as far as La Belle Alliance, in front of the Waterloo position, a distance of about sixteen or seventeen miles; and this, too, in rear of a victorious Army, with a Cavalry Rear Guard boldly and successfully impeding the advance of its pursuers. It must, however, be taken into account, that in one most important respect NAPOLEON possessed a decided advantage over GROUCHY--an advantage, the magnitude of which increased with every moment that elapsed after the wet weather had set in; for while the former moved the whole distance along a paved high road, the latter had to proceed entirely by cross roads, which may more properly be designated common field roads. It is to this particular point that both GROUCHY and GÉRARD refer in justification of the late arrival of the Infantry at Gembloux. Nevertheless, GROUCHY detached considerably to his Right, with his Cavalry, misled by the same idea which had prevailed with NAPOLEON, that BLÜCHER had retreated upon the Meuse; and the very circumstance of his Dragoons having reached Perwès on the night of the 17th, proves that had he organised a more extended, more combined, and more energetic reconnaissance, with the sixty five Squadrons of Cavalry which had been placed under his orders, he might have connected his operations on the right of the Dyle with those of NAPOLEON on the left of that river, by occupying the line of Nil St Vincent, Corbaix, Mont St Guibert, and the Bridge of Moustier. The only check he would have experienced would have been at the Prussian Post of Mont St Guibert; which, however, in the case of an active reconnaissance, as above, might have been attacked by a strong Detachment in front, and turned by Corbaix on its left.