Napoleon had reached Frasnes at nine o’clock on the morning of the 17th, and determined on attacking the allied commander. Still uncertain as to the route by which Blucher was retiring, he detached Grouchy in pursuit with the third and fourth corps, and the cavalry of Excelmans and Pajol, with directions to overtake the Prussian marshal, if possible, and in that case bring him to action. While Buonaparte delayed his attack until his reserve and the sixth corps came up, his abler antagonist was preparing to retire. This operation in open day was difficult, as the Dyle was in the rear of the allies, and the long and narrow bridge at the village of Genappe the only means by which the _corps d’armée_ could effect its passage. Wellington disposed some horse-artillery and dismounted dragoons upon the heights, and leaving a strong rear-guard in front of Quatre Bras, he succeeded in masking his retreat until, when discovered, it was too late to offer any serious interruption to the regressive movement of the allies. While the rear of the columns were still defiling through the narrow streets of Genappe, Napoleon’s advanced cavalry overtook and attacked the rear-guard, and a sharp affair ensued. The 7th Hussars, assisted by some squadrons of the 11th and 23rd Light Dragoons, charged the French horsemen boldly--but they were repulsed; and a second effort was bravely but ineffectually attempted. The Life Guards were instantly ordered up, and led in person to the charge by Lord Anglesea, who was in command of the British rear-guard. Their attack was decisive--the enemy were severely checked, and driven in great disorder back upon their supports. No other attempt was made by the French cavalry to embarrass the retreat of the allied columns--and except by an occasional cannonade, too distant to produce any serious effect, the remainder of the march on Waterloo was undisturbed by the French advance. The allies reached the position early in the evening, and orders were issued for the divisions to halt and prepare their bivouacs. The ground for each brigade had been already marked out--the troops piled their arms,--the cavalry picketed their horses--the guns were parked-- fires were lighted along the lines, and all prepared the best mode of sheltering themselves from the inclemency of the weather, which scanty means could afford them in an exposed position like that of Waterloo. All through the day rain had occasionally fallen--but as night came on, the weather became more tempestuous. The wind rose, and torrents of rain, with peals of thunder and frequent lightning, rendered the dreary night before the battle anything but a season of repose.