On the tenth day of August Bouchain was invested, and the duke of Marlborough exerted himself to the utmost extent of his vigilance and capacity, well knowing the difficulties of the undertaking, and how much his reputation would depend upon his success. Villars had taken every precaution that his skill and experience could suggest, to baffle the endeavours of the English general. He had reinforced the garrison to the number of six thousand chosen men, commanded by officers of known courage and ability. He made some efforts to raise the siege; but they were rendered ineffectual by the consummate prudence and activity of the duke of Marlborough. Then he laid a scheme for surprising Douay, which likewise miscarried. If we consider that the English general, in the execution of his plan, was obliged to form lines, erect regular forts, raise batteries, throw bridges over a river, make a causeway through a deep morass, provide for the security of convoys against a numerous army on the one side, and the garrisons of Condé and Valenciennes on the other, we must allow this was the boldest enterprise of the whole war; that it required all the fortitude, skill, and resolution of a great general, and all the valour and intrepidity of the confederate troops, who had scarce ever exhibited such amazing proofs of courage upon any other occasion as they now displayed at the siege of Bouchain. In twenty days after the trenches were opened, the garrison were obliged to surrender themselves prisoners of war; and this conquest was the last military exploit performed by the duke of Marlborough: the breaches of Bouchain were no sooner repaired than the opposite armies began to separate, and the allied forces were quartered in the frontier towns, that they might be at hand to take the field early in the spring. They were now in possession of the Maese, almost as far as the Sambre; of the Schelde from Tournay; and of the Lys as far as it is navigable. They had reduced Spanish Guelderland, Limburg, Brabant, Flanders, and the greatest part of Hainault; they were masters of the Scarpe; and by the conquest of Bouchain, they had opened to themselves a way into the very bowels of France. All these acquisitions were owing to the valour and conduct of the duke of Marlborough, who now returned to the Hague, and arrived in England about the middle of November.