By nightfall, therefore, on Saturday the 17th of June, we have the mass of the Prussian army safe round Wavre, and duly disposed all round that town in perfect order. With the exception of a rearguard, which did not come up until the morning of the Sunday, all had been safely withdrawn in the twenty-four hours that followed the defeat at Ligny. It may be asked why this great movement had been permitted to take place without molestation from the victors. [Illustration] Napoleon would naturally, of course, after his defeat of the Prussians, withdraw to the west the greater part of the forces he had used against Blucher at Ligny and direct them towards the Brussels road in order to use them next against Wellington. But Napoleon had left behind him Grouchy in supreme command over a great body of troops, some 33,000 in all, whose business it was to follow up the Prussians, to find out what road they had taken; at the least to watch their movements, and at the best to cut off any isolated bodies or to give battle to any disjointed parts which the retreat might have separated from support. In general, Grouchy was to see to it that the Prussians did not return. In this task Grouchy failed. True, he was not given his final instructions by the Emperor until nearly midday of the 17th, but a man up to his work would have discovered the line of the Prussian retreat and have hung on to it. Grouchy failed, partly because he was insufficiently provided with cavalry, partly because he was a man excellent only in a sudden tactical dilemma, incompetent in large strategical problems, partly because he mistrusted his subordinates, and they him; but most of all because of an original prepossession (under which, it is but fair to him to add, all the French leaders lay) that the Prussian retreat had taken the form of a flight towards Namur, along the eastern line of communications, while, as a fact, it had taken the form of a disciplined retreat upon Wavre and the north.