Grouchy had orders to take Vandamme’s Corps and Excelmans’ Cavalry, and pursue the Prussians along the Charleroi-Fleurus road; but he was deceived as to the strength of the enemy at Gilly. Fearing to attack without further reinforcements, he rode back to Napoleon for instructions. This was at about 5 P.M. Napoleon, fretting at the delay, which he regarded as needless, himself rode out with four squadrons of Cavalry of the Guard, and reconnoitred Pirch’s position. He soon satisfied himself as to Pirch’s real strength, and gave Grouchy orders to attack at once. Accordingly, at 6 P.M., artillery fire opened on the Prussians from two batteries; three infantry columns from Vandamme’s Corps were ordered to assault in front, and two cavalry brigades to menace the Prussian flanks. Pirch was preparing to reply to the French artillery fire, when he received orders from Zieten to retire on Fleurus _viâ_ Lambusart. As soon as he began to withdraw his battalions, the French cavalry, under Letort, made a vigorous attack. The Prussian infantry resisted stoutly, and a regiment of dragoons, with great boldness, charged the French squadrons with such effect that they were for the moment checked, and the Prussians were able to gain the cover of the wood of Fleurus. A battalion of the Sixth Regiment of the Line, by forming square repeatedly, bravely kept the enemy’s cavalry at a distance, and gained very valuable time for the retreat of the rest of Pirch’s Division. In front of Lambusart, where Pirch joined some battalions of the Third Division and Roder’s Reserve Cavalry, a fresh position was taken up, and a regiment of Brandenburg Dragoons, sent by Zieten to support Pirch II., did excellent service by charging the French horsemen and checking their pursuit. Towards eight o’clock three batteries of French Horse Artillery, which accompanied the cavalry, opened fire on Lambusart; but night was coming on, and the attack died out very shortly afterwards. Pirch II. then withdrew to Fleurus, where he joined the remainder of Zieten’s Divisions, and the whole Corps retreated to Ligny. Steinmetz had reached Fleurus from Heppignies at about 10 P.M. Zieten’s retreat in the face of almost the whole French army is worthy of close attention. His men had been marching and fighting from three o’clock in the morning until ten o’clock at night, and had engaged the enemy in one or two very sharp conflicts. The skilful manner in which each Division was withdrawn without getting too closely engaged with the enemy, and in which the Divisions supported each other, is illustrative of the best methods of war. That he was able to concentrate his Corps at Fleurus with a loss of only 1,200 men, after having checked the rapid onset of the French, speaks very highly for Zieten’s skill in generalship. The campaign of Waterloo still affords useful lessons and examples to modern students.