The siege of Bouchain (9 August – 12 September 1711), following the Passage of the Lines of Ne Plus Ultra (5 August 1711), was a siege of the War of the Spanish Succession, and the last major victory of John Churchill, 1st Duke of Marlborough. Marlborough and François Nicolas Fagel broke through the French defensive lines and took Bouchain after a siege of 34 days. Its capture left Cambrai the only French-held fortress between the allied army and Paris. Prelude Throughout the early summer of 1711 Marlborough's army, having taken the important fortress of Douai the previous year, manoeuvred indecisively in northern France, blocked by the French Lines of Ne Plus Ultra – a massive series of fieldworks stretching from the Channel coast to the Ardennes at Namur. The allied army had been weakened by the withdrawal of Prince Eugene's army to cover the upper Rhine, as the deposed Elector of Bavaria attempted to take advantage of the disruption caused by the death of the Emperor Joseph. On 6 July, Marlborough captured the small fortress of Arleux, just to the north of the Lines, west of Bouchain, both to deny its use to the French as a sally-port, and to secure the water supply to Douai, which could be cut off by damming the canal that supplied the town. The Duke was then wrong-footed by Villars as the French army crossed the Lines on 22/23 July and retook Arleux, with the allied army too far to the west to intervene in time, and the defences were levelled before the French retreated back across the Lines. Marlborough, initially furious, soon retook the initiative by marching his army as if to assault the Lines near Arras, and carrying out a detailed personal reconnaissance there on 4 August in full view of Villars' covering army. That night the army struck camp, leaving their campfires burning to deceive the French, and marched eastwards to Arleux. At midnight a force from Douai under Cadogan crossed the unguarded French lines, and by 8 am the advance guard of the main army was also crossing over. Villars, arriving on the scene with a few hundred cavalry, realised he had been outmanoeuvred, and though he attempted to offer battle in front of Bourlon Wood, Marlborough declined to attack, the Marshal's position being even stronger than the one in which he had given Marlborough's army such a mauling two