He ordered Excelmans’ Cavalry and Vandamme’s Corps to march to Sart à Walhain; Gérard’s Corps to follow Vandamme’s to Sart à Walhain, and the Seventh Cavalry Division to push on to Grand Leez; Pajol’s force to march from Le Mazy to Grand Leez. (Pajol had reached St Denis, half-way from Le Mazy to Grand Leez, on the 17th, so that he now had covered this ground twice.)
When Bonnemain’s reports to Excelmans reached Grouchy, he should have had no longer any doubts as to the true line of Blucher’s retreat. Towards half-past two in the morning, news from Walhain came in, to the effect that the peasants there had reported that about three Prussian Corps had passed through on the previous day, marching in the direction of Wavre. A glance at the map will show that Gembloux to Walhain is in the direction of Wavre, and not of Liège. Further, from information gathered by the peasants from Prussian stragglers and the gossips who seem to find a place in every army, the enemy were talking of the coming battle near Brussels. As to Grouchy’s thoughts, and the influence these reports had on him, it is difficult to find what train of reasoning he followed. He knew that Napoleon expected to fight Wellington near the Forest of Soignies: he knew, too, that the Emperor was anxious for him to prevent the Prussians from marching across to join the English, yet he did not consider the very great possibility that Blucher might rapidly join Wellington by a short flank march from Wavre. Had such a possibility entered his mind, he must have reflected on the best means of thwarting it, ere it became too late. Obviously his only move then was to make for the bridges at Moustier and Ottignies, _viâ_ Saint Géry. By reaching the left bank of the Dyle (which he could easily do before Blucher), Grouchy could have either manœuvred to join Napoleon, when an addition of 33,000 troops must have overwhelmed Wellington, or he could have continued to pursue the Prussians, should it happen that he had been wrong in supposing that they were marching to join the English. It did not require extraordinary foresight or mental effort to realize how much more useful and how much more effective a move _viâ_ St Géry and Moustier and the left bank of the Dyle would have been. If Grouchy was really as undecided as he appears to have been, as to the Prussian line of retreat, he should have had recourse to a movement which offered no doubtful advantages. A move across the Dyle by Moustier would have had a very great effect, and if the Prussians had really retreated on Liège, this movement of Grouchy’s would still have its advantages. He could have thrown his weight into the fight at Waterloo; Napoleon would not blame him for this assistance, if he knew that the Prussians were out of reach.