It remains to be seen whether Grouchy, acting on Gérard's advice, could have saved the defeat of Waterloo. He had to take 33,000 men with all their guns and ammunition waggons across the river Dyle, by two bridges, one narrow and steep, the other of wood and presumably not strong enough for artillery. He had to march fourteen or fifteen miles by very bad country roads, rendered much worse by the rain. The Prussians from Wavre had a shorter distance to go with no river to cross, and the foremost corps, Bulow's, had considerably the start: the head of his column was in sight of the battle-field when Grouchy's resolution was taken. Moreover one corps, Ziethen's, took a parallel road further to the north, entirely out of Grouchy's reach. It is pretty certain that if Grouchy had marched on Waterloo, he would have prevented Pirch's corps, which followed Bulow's, from taking part in the battle, and so would have rendered the rout a little less absolute. It is pretty certain also that Bulow need have taken no notice of him, but it is not so clear that he might not have been sufficiently disquieted by Grouchy's appearance to think it expedient to turn back and encounter him. Blucher however was with Bulow's corps, and he was eager to press forward, at whatever cost. If Napoleon had been in Blucher's place, he would have seen that the defeat of the enemy's main army was of primary importance, and would have taken his chance of Grouchy achieving some success against the Prussians left behind. It is however unprofitable to conjecture what might have been. Happily for Wellington and for Europe, Grouchy was afraid to face the responsibility, and marched on Wavre. Here, to finish his story, he encountered Thielemann's corps, left to play against him the very game which Napoleon intended him to play against the whole Prussian army, to detain and occupy as much as possible a superior force. There was some fighting on the evening of the 18th, and again on the next morning, to the advantage of the French. But when Grouchy heard of the total defeat of the emperor, he naturally thought only of regaining France. His retreat was conducted with skill and audacity, and ended, thanks to the protection afforded him in crossing the Meuse by the fortifications of Namur, in his reaching French territory with his army unbroken.