This despatch had hardly been handed to the staff-officer[592] who was to carry it to the Emperor, when the cannon of Waterloo was heard. Then, at any rate, Marshal Grouchy knew that the English were not retreating before Napoleon, but were standing “on this side of the Forest of Soignes,” as the Emperor had, the afternoon before, conjectured they might. Three Prussian corps had gone towards Brussels, as Grouchy had just written to the Emperor. It was very possible that they might at that moment be marching across the country to join the Anglo-Dutch army. Perhaps nothing could prevent this. But it was plainly Grouchy’s duty to march towards the Emperor as fast as he could. If he could not prevent the Prussians from joining the English, he might at any rate be able to prevent them from attacking the French. If he should cross the Dyle at Moustier and Ottignies, and move directly towards the line of march which they must take in order to attack the French, their march would, if he arrived in time, assuredly be suspended. This was at any rate the thing to try to do. It was to be feared that a terrible disaster was impending over Napoleon and his army; but there was a chance of averting it. There was only one thing to do,—and that was, promptly and gallantly to make the attempt to avert it. (See Map 10.) Gérard, who had arrived at Walhain with his corps, strenuously urged Grouchy to march to the sound of the cannon. He pressed this on Grouchy with perhaps undue heat; but the occasion was one that admitted of no delay. The son of Marshal Grouchy, who may be supposed to have heard his father’s account of the interview, says:—[593] “The commander of the 4th Corps uttered haughtily, and in a fashion little in harmony with the respect due to his chief and with military discipline, the advice that the right wing ought to march to the sound of the cannon in order to effectuate a junction with the Emperor. “Grouchy did not find the advice bad in itself, but the form employed to present it. At the same time he consented to discuss Gérard’s opinion with him.” That personal feelings had some influence on Marshal Grouchy’s decision would seem from the above statement very probable.[594] We do not reproduce the arguments of Marshal Grouchy here, because they are based mainly upon his statement, which we have found to be erroneous, that “his instructions, from which he was not permitted to depart, enjoined formally upon him not to lose sight of the Prussians when he should have joined them.” A discussion where one of the parties concealed the existence of a written order, which prescribed no such instructions as those stated above, cannot enlighten us much.