While the Emperor was making the round of his outposts, a somewhat cryptic despatch from Grouchy reached headquarters.  The Marshal reported from Gembloux, at 10 p.m. of the 17th, that part of the Prussians had retired towards Wavre, seemingly with a view to joining Wellington; that their centre, led by Bluecher, had fallen back on Perwez in the direction of Liege; while a column with artillery had made for Namur; if he found the enemy’s chief force to be on the Liege chaussee, he would pursue them along that road; if towards Wavre, he would follow them thither “in order that they may not gain Brussels, and so as to separate them from Wellington.”  This last phrase ought surely to have convinced Napoleon that Grouchy had not fully understood his instructions; for to march on Wavre would not stop the Prussians joining Wellington, if they were in force.[503]

Moreover, Napoleon now knew, what Grouchy did not know, that the Prussians were in force at Wavre.  It seems strange that the Emperor did not send this important news to his Marshal; but perhaps we may explain this by his absence at the outposts.  As it was, no clear statement of the facts of the case was sent off to Grouchy until 10 a.m. of the 18th.  He then informed his Marshal that, according to all the reports, three bodies of Prussians had made for Wavre.  Grouchy “must therefore move thither—­in order to approach us, to put yourself within the sphere of our operations, and to keep up your communications with us, pushing before you those bodies of Prussians which have taken this direction and which may have stopped at Wavre, where you ought to arrive as soon as possible.”  Grouchy, however, was not to neglect Bluecher’s troops that were on his right, but must pick up their stragglers and keep up his communications with Napoleon.

Such was the letter; and again we must pronounce it far from clear.  Grouchy was not bidden to throw all his efforts on the side of Wavre; and he was not told whether he must attack the enemy at that town, or interpose a wedge between them and Wellington, or support Napoleon’s right.  Now Napoleon would certainly have prescribed an immediate concentration of Grouchy’s force towards the north-west for one of the last two objects, had he believed Bluecher about to attempt a flank march against the chief French army.  Obviously it had not yet entered his thoughts that so daring a step would be taken by a foe whom he pictured as scattered and demoralized by defeat.[504]

As we have seen, the Prussians were not demoralized; they had not gone off in three directions; and Bluecher was not making for Liege.  He was at Wavre and was planning a master-stroke.  At midnight, he had sent to Wellington, through Mueffling, a written promise that at dawn he would set the corps of Buelow in motion against Napoleon’s right; that of Pirch I. was to follow; while the other two corps would also be ready to set out.  Wellington received