Napoleon and Soult, therefore, one would suppose, might have seen by the programme which Grouchy had marked out for himself in his despatch that in all probability he was not clearly apprehending the situation, and that it was therefore possible that he might make a serious, perhaps a very serious, mistake the next day. They ought, therefore, if they suspected this to be the state of the case, to have replied at once, giving him precise instructions as to his course in the event of the retreat of the Prussians on Wavre. They should have told him, that, if he should find this to be the fact, he must at once march to cross the Dyle above Wavre, at Moustier and Ottignies, approach the main army, and act in conjunction with it. Yet although Grouchy told the officer who carried the 10 P.M. despatch to wait for an answer, none was returned.[561] Grouchy was not even informed where the army was, and that it was confronted by the English army in position. Nor was he advised, as he surely should have been, that Domon’s reconnoissance had proved that a strong Prussian column,—consisting, as we have seen, of the two beaten corps, those of Zieten and Pirch I.,—had retired on Wavre by way of Gery and Gentinnes.[562] It is impossible to account for these omissions.[563] Now this last-mentioned fact, that “a pretty strong (Prussian) column” had “passed by Gery and Gentinnes, directed on Wavre,” was the most important fact that could be ascertained, both for Napoleon and Grouchy. Napoleon had in fact, at 2 A.M. of the 18th, when Grouchy’s letter arrived, strong reason to apprehend that Grouchy might, during the night, ascertain that the whole of Blücher’s army had retired on Wavre. It certainly would seem that this was one of those cases where nothing should be omitted that could assist the mind of a subordinate in arriving at a correct conclusion.[564] Napoleon, however, seems to have thought it unnecessary to send Grouchy any precise directions. We know that he expected Grouchy to arrive the next afternoon by the bridge of Moustier. Marbot, whose Memoirs have just been published, states,[565] that, towards 11 A.M. of the day of the battle, he was sent with his own regiment of hussars and a battalion of infantry to and beyond the extreme right of the army, with instructions, brought to him by one of the Emperor’s aides, to push reconnoissances to the bridges of Moustier and Ottignies. He says that these detachments were connected by cavalry-posts, “so that they could quickly inform him of their junction with the advance guard of the troops of Marshal Grouchy, which were to arrive on the Dyle.”