It was to prevent a dangerous flank movement of the enemy--the advance, namely, of Bülow, with the cavalry corps of Prince William, upon Plancenoit--that Napoleon had detached the young guard, under Duhesme, a third of his precious reserve, for the support of Lobau's right; Durutte being in the rear of his left, that portion was already as strong as it could be made. Nevertheless the Prussians seized Plancenoit; at once the French rallied, and drove them out; Blücher threw in eight fresh battalions, and these, with the six already engaged, dashed for the ravine leading to the village. The passage was lined with French, and for a time it was like the valley of Hinnom; but the Prussians pressed on, and the young guard reeled. Napoleon sent in two battalions of the old guard, under Morand and Pelet; their firmness restored that of their comrades, and the place was cleared, two thousand dead remaining as the victims of that furious charge and countercharge. At seven Bülow was back again in his first position, awaiting the arrival of Pirch's corps to restore his riddled ranks. Napoleon had now left only twelve of the twenty-three battalions of the guard reserve, less than six thousand men. Wellington had repaired the breach made by Ney, and, though still hard pressed on his right, Ziethen had made good the strength of his left, whence some of his cavalry, the brigades of Vivian and Vandeleur, had been detached to repair other weak spots in the line. At this moment Ziethen conceived that Bülow was further giving way, and hesitated in his advance. The brief interval was noted by Durutte, and with a last desperate effort he carried Papelotte, La Haye, and Smohain, hoping to prevent the fatal juncture. It was half an hour before Ziethen retrieved his loss, and thus probably saved Wellington's left. By that time Pirch had come up, and with this reinforcement Bülow, behind the heavy fire of his powerful batteries, charged Lobau, and advanced on the guard at Plancenoit. Lobau, the hero of Aspern, stood like a rock until Durutte's men and the remnants of d'Erlon's corps, flying past his flank, induced a panic in his ranks. Thereupon the whole French right fell into confusion: all except the guard, who stood in the churchyard of Plancenoit until surrounded and reduced in number to about two hundred and fifty men; then, under Pelet's command, they formed a square, placed their eagle in the midst, drove off the cavalry which blocked their path, and reached the main line of retreat with scarcely enough men to keep their formation. The name of Ziethen must stand in equal renown with that of Colborne among the annals of Waterloo. The rout of the French left was the beginning of Napoleon's calamity, as that of his right under Colborne was its consummation.