Accordingly, a little before midnight on the 17th of June, during a heavy rain, the army struck its tents, and the FOURTH HORSE, composing part of twenty squadrons destined to cover the movement, formed up to confront the enemy, while the army commenced the retreat, which was continued throughout the night without interruption from the French, and it re-crossed the Saar and the Moselle on the following day. On the 19th the retreat was resumed, and on the 25th the FOURTH HORSE and other cavalry arrived at Duren, in the duchy of Juliers. At the same time the French troops, near the Dutch frontiers, ceased acting on the offensive, and retired in a panic to Tongres. After this long and difficult march, the FOURTH HORSE crossed the Maese near Viset, and were subsequently employed in covering the siege of _Huy_, which the enemy had retaken during the absence of the army up the Moselle. The French army having taken refuge behind their fortified lines, the Duke of Marlborough, after the surrender of _Huy_, resolved to attempt to surprise them in their formidable barrier, the construction of which had employed the space of three years. He accordingly, by a skilful manœuvre, succeeded in dividing their forces and in drawing them from the point selected for the attack. About eleven o'clock on the evening of the 17th of July the FOURTH HORSE, forming part of the division destined to force the lines, left their camp ground and continued their march throughout an extremely dark night, until about four the next morning, when the heads of columns approached the works at _Neer-Hespen_ and _Helexim_. The guards were surprised and fled in a panic, the lines were forced and partly levelled, and the British horse were soon within the barriers; but before the regiments were formed, the Marquis d'Allegre appeared with fifty squadrons of cavalry and twenty battalions of infantry, and opened a cannonade from eight pieces of artillery. After the allied infantry had fired a few rounds, the Duke of Marlborough led forward the cavalry, which had passed the works, and the gallant British horsemen, by an impetuous charge, broke the enemy's ranks. The victorious squadrons afterwards sustained some loss from the fire of the enemy's infantry, but a second charge decided the combat; the hostile cavalry were routed and dispersed, several battalions of infantry were cut to pieces, many prisoners, standards, and colours were taken, and the FOURTH HORSE were once more triumphant over the legions of France and Spain.[31]