In the summer of 1711, the imperialists, under Prince Eugene, having returned to Germany, the Duke of Marlborough confronted the French army with the forces under his orders. The French had constructed very extensive and strong lines of fortifications to cover their frontiers, and within these lines they had collected a numerous army. The Duke, by a skilful device, induced them to destroy their fort at Arleux; and then, by menacing their lines between the head of the Sanzet and Hesdin, caused them to withdraw part of their garrisons from Arras and Cambray, with the troops which guarded the lines in the direction of Arleux. In the mean time his grace was continually sending detachments towards Douay, where a considerable body of troops was assembled without attracting notice, and amongst these forces were the two squadrons of CADOGAN'S CUIRASSIERS. Having reconnoitred the lines on the 4th of August, the Duke gave orders for the troops to prepare for the attack on the following morning, and the French army prepared to receive him with eclat; but at the dead of the night, Lieutenant-General Cadogan, having advanced with great secrecy with the troops from Douay, passed the lines at the causeway of _Arleux_, which the French commander, in his anxiety to collect all the troops he could to resist the menaced attack, had left unguarded; and the main army struck its tents in the night, and marched in the same direction. When Marshal Villiers heard that his lines were passed, he was astounded. He took with him the household cavalry, and, ordering his army to follow as quickly as possible, rode with all speed, until he came within the English out-guards, and his feelings were so excited, that he was nearly surrounded by a troop of CADOGAN'S HORSE before he was conscious of danger; he had proceeded with such rapidity that the whole of his escort, except a hundred of the best mounted dragoons, was left behind; he ordered these dragoons to throw themselves into the old castle of Oisy, which was at hand, and himself and two officers of his staff escaped; but the dragoons were surrounded and made prisoners.