Tournay had been fortified by Vauban and was one of the strongest fortresses in France,[60] but its garrison had been weakened by the unsuspecting Villars, and there was little hope for it. The heavy artillery of the Allies, which had been sent to Menin, went down the Lys to Ghent and up the Scheldt to the besieged city, the trenches were opened on the 7th of July, ◆June 26./July 7.◆ and after three weeks, despite of the demonstrations of Villars and incessant heavy rain, Tournay was reduced to surrender.[61] ◆July 19/28.◆ Then followed the siege of the citadel, the most desperate enterprise yet undertaken by the Allied troops, inasmuch as the subterraneous works were more numerous and formidable than those above ground. The operations were, therefore, conducted by mine and countermine, with destructive explosions and confused combats in the darkness, which tried the nerves of the soldiers almost beyond endurance. The men did not object to be shot, but they dreaded to be buried alive by the hundred together through the springing of a single mine.[62] Four English regiments[63] bore their share in this work and suffered heavily in the course of it, until on the 3rd of September the citadel capitulated. ◆Aug. 23./Sept. 3.◆ Before the close of the siege Marlborough and Eugene, leaving a sufficient force before Tournay, had moved back with the main army before the lines at Douay. They had long decided that the lines were far too formidable to be forced, but they saw no reason for communicating this opinion to Villars. ◆Aug. 20/31.◆ On the 31st of August Lord Orkney, with twenty squadrons and the whole of the grenadiers of the army, marched away silently and swiftly eastward towards St. Ghislain on the Haine. ◆Aug. 23./Sept. 3.◆ Three days later, immediately after the capitulation of the citadel of Tournay, the Prince of Hessen-Cassel started at four o’clock in the afternoon in the same direction; at nine o’clock Cadogan followed him with forty squadrons more, and at midnight the whole army broke up its camp and marched after them. Twenty-six battalions alone were left before Tournay to superintend the evacuation and to level the siege-works, with orders to watch Villars carefully and not to move until he did.