The British army retreated upon Waterloo almost unmolested. Ney was probably awaiting orders, and Napoleon, believing the Prussians to be at Namur, probably thought he might safely rest himself and his army before crushing Wellington at his leisure. When they realised that Wellington was deliberately moving his army to a position nearer Brussels, they both followed in pursuit along different roads converging at Quatre Bras, and a brisk skirmish took place near Genappe between Ney's cavalry and that of the British rear-guard. Heavy rain came on, and the two armies spent a miserable night, half a mile from each other, close to Mont St. Jean, and south of Waterloo. Napoleon rose before daybreak on the 18th, reconnoitred the British position, and convinced himself that Wellington intended to give battle. He expressed to his staff his satisfaction and confidence of victory, when General Foy, who had experience of the Peninsular war, replied in significant words: "Sire, when the British infantry stand at bay, they are the very devil himself". Why Napoleon did not begin the battle at eight o'clock has been the subject of much discussion. It is said that he waited for Grouchy to join him before the close of the action. But neither he nor Grouchy, though aware that at least a large force of Prussians had gone to Wavre and not to Namur, suspected that Blücher had promised Wellington to march with his whole army on the morning of the 18th to support the British at Waterloo. It is more likely that he waited for his men to assemble and for the ground to dry and become more practicable for his powerful artillery.[62]