These made a charge like that which had borne down the Austrians at Marengo, but the British squares were proof against it, and when a division of guards came up from Nivelles, the French in turn were put on the defensive and retreated to Frasnes. The loss on the British side was 4,500 men; that on the French somewhat less. It is not difficult to imagine what the issue of the battle must have been if D'Erlon's corps had been brought into action. This corps was occupied in marching and countermarching, under contradictory orders from Napoleon and Ney, between the British left and the Prussian right during the whole of this eventful day. Its appearance in the distance just when Napoleon was about to launch his guard against the Prussians at Ligny, caused him to hesitate long, and lose the decisive moment for demolishing his enemy. Its failure to appear at Quatre Bras, and to roll up the wavering Dutch-Belgians, before Picton took up the fighting, enabled Wellington to hold his ground at first, to repulse Ney afterwards, and on hearing of Blücher's defeat at Ligny, to fall back in good order on Waterloo. Even then, something was due to good fortune. Had Napoleon joined Ney and marched direct on Quatre Bras early on the 17th, it is difficult to see how his advance to Brussels could have been arrested. But whether he was exhausted by his incessant labours since leaving Paris, or whether his marvellous intuition was deserting him, certain it is that he allowed that critical morning to slip by without an effort--and without a reconnaissance. He assumed that Blücher must retire upon Namur as his base of operations, and that Wellington, retiring towards Brussels, would be cut off from his allies. He therefore despatched Marshal Grouchy, with 33,000 men, to follow up the Prussians eastward by the Namur road. His assumption was unfounded. Blücher, loyal to his engagements, retired upon Wavre; Wellington, relying upon Blücher's loyalty, took his stand on the field of Waterloo; and this error on the part of Napoleon determined the fortunes of the campaign.[61] [Pageheading: _WATERLOO._]