Bouchain was one of the most impregnable fortresses remaining in French hands. The 5,000 defenders were supported by Villars and the French army of 100,000 men with their headquarters only two miles away. A number of skirmishes in strength failed to bring Villars to battle. The Allies achieved some remarkable feats of engineering to neutralise the hill of Wavrechin and the lines of circumvallation were begun on the 12th August. By the 23rd August some 30 miles of entrenchments had been completed around the fortress and trenches which pushed forwards were begun. The seige train of 30 heavy cannon and 30 mortars arrived on the 21st and were in action as grand batteries on the 30th. A number of attempts by Villars and by the garrison to break the seige all came to nought and by the 11th September two breaches in the main defences were open for assault. On the 12th the Governor tried to negotiate for terms of surrender but Marlborough refused all proposals until later that day de Ravignau surrendered unconditionally. On the 13th twenty four colours and all arms were handed over, de Ravignau and his men were made prisoners of war.

Town of Bouchain, north eastern France. At the confluence of the Scheldt and the Scarpe. (France)

After the brilliant series of movements by which the Allied army penetrated the lines of 'Non Plus Ultra' Marlborough withdrew to invest the fortress of Bouchain.