Seen from the point where Napoleon stood to the rear of his line, the high place that overlooked the battlefield, it seemed to eyes of less genius than his own that this second attempt had succeeded. Indeed, its fierce audacity seemed to other than the French observers at that distance to promise success. The drivers of the reserve batteries in the rear of Wellington's line were warned for retreat, and Napoleon, reluctant, but pressed by necessity, seeing one chance at last of victory by mere shock, himself sent forward a reserve of horse to support the distant cuirassiers and lancers. He called upon Kellerman, commanding the cavalry of the Guard, to follow up the charge. He knew how doubtful was the success of this last reinforcement, for he knew how ill-judged had been Ney's first launching of that great mass of horse at an unbroken enemy; but, now that the thing was done, lest, unsupported, it should turn to a panic which might gain the whole army, he risked almost the last mounted troops he had and sent them forward, acting thus like a man throwing good money after bad for fear that all may be lost. A better reason still decided Napoleon so to risk a very desperate chance, and to hurl Kellerman upon the heels of Milhaud. That reason was the advent, now accomplished, of the Prussians upon his right, and the necessity, imperative and agonised, of breaking Wellington's line before the whole strength of the newcomers should be felt upon the French flank and rear. Let us turn, then, and see how far and with what rapidity the Prussians at this moment--nearly half-past five o'clock--had accomplished their purpose. * * * * * Of the four Prussian corps d'armée bivouacked in a circle round Wavre, and unmolested, as we have seen, by Grouchy, it was the fourth, that of Bulow, which was given the task of marching first upon the Sunday morning to effect the junction with Wellington. It lay, indeed, the furthest to the east of all the Prussian army,[22] but it was fresh to the fight, for it had come up too late to be engaged at Ligny. It was complete; it was well commanded.