Blücher had decided, in the event of an advance by the French across the line of the Sambre, by Charleroi, upon concentrating his Army in a position in front of Sombref, a point upon the high road between Namur and Nivelles, above fourteen miles from the former place, and only seven miles and a half from Quatre Bras, the point of intersection of this road with the one leading directly from Charleroi to Brussels, and at which Wellington had agreed, in that case, to concentrate as large a force as time would admit, in order to check any advance in this direction, or to join Blücher's Right Flank, according to circumstances.
Blücher
Should the Enemy advance along the left bank of the Meuse towards Namur, this place would become the point of junction of the First, Second, and Fourth Corps of the Prussian Army, whilst the Third, collecting at Ciney, would, after presenting a stout resistance at Dinant, operate as effectively as circumstances would admit, against the Right of the line of attack; and should he advance by the right bank of the Meuse towards Ciney, the Army would concentrate at this point, with the exception of the Fourth Corps, which would assemble at Liege as a Reserve, for the better security of the Left Flank and of the communications with the Rhine.
Such were the dispositions of the Allied Commanders, who contemplated no change in their arrangements until the moment should arrive of the commencement of hostile demonstrations of a decided character, for which they were perfectly prepared, and for which a vigilant look-out was maintained along the general line of the Advanced Posts.
From the foregoing, however, it would appear that the concentration of Wellington's Army on its own Left, and that of Blücher's Army on its own Right, required longer time than that in which they could have been respectively accomplished on other points; and further that the distribution of the former was better calculated to meet the Enemy's advance by Mons, and that of the latter to meet it by Namur, than to oppose a line of attack by Charleroi. This peculiar feature in the dispositions of the two Commanders did not escape the vigilance of Napoleon, who, as will be seen in the sequel, made it subservient to his hopes of beating their Armies in detail.