[Footnote 20: For the text of the order to d'Erlon and a full discussion of the whole subject, see Houssaye, 1815, p. 201.] Bluecher, who was determined to fight, come what would, had held in as long as his impatient temper permitted; but when no reinforcement from Wellington appeared, he first fumed, and then about six gave his fatal orders to prepare for the offensive. The nature of the ground was such as necessarily to weaken his center by the initial movements. Napoleon marked this at once, and summoned his guard in order to break through. For a moment the Emperor hesitated; a mysterious force had appeared on the left; perhaps they were foes. But when once assured that they were d'Erlon's men, he waited not an instant longer; at eight the crash came, and the Prussian line was shattered. Retreat was turned into a momentary rout so quickly that Bluecher could not even exchange his wounded horse for another, and in the first mad rush he was so stunned and overwhelmed that his staff gave him up for lost. The few moments before he was found were the most precious for the allies of the whole campaign, since Gneisenau directed the flight northward on the line to Wavre, a route parallel with that on which Wellington, whatever his success, must now necessarily withdraw. This move, which abandoned the line to Namur, is Gneisenau's title to fame.[21] The lines were quickly formed to carry it out, and the rest of the retrograde march went on with great steadiness. Napoleon did not wait until d'Erlon arrived and thereupon order an immediate, annihilating pursuit, but came to the conclusion that the Prussians were sufficiently disorganized, and would seek to reorganize on the old line to the eastward. They were thus, he thought, completely and finally cut off from Wellington. It was not until early next morning that he despatched Pajol, with his single cavalry corps, to follow the foe, for he was confirmed in his fatal conjecture by the false report of five thousand Prussians having been seen on the Namur road, and exerting themselves to hold it. The Prussians seen were merely a horde of stragglers. The truth was not known until next day. [Footnote 21: Long regarded as a more or less haphazard decision, it has been established at last that the officers of the Prussian general staff were able by the light of a horn lantern so to exhibit their maps, explain their study of the ground, and develop the necessary strategy as to determine with considerable accuracy where they were and what the scientific move should be. When this was duly set forth in the history of the general staff, the exultation of the Emperor William II was expressed in his public speeches, and the Germans of the empire were convinced that by this decision the result of the Waterloo campaign was determined.]