Cadogan, a superb cavalry commander, ordered some dragoons under the command of Danish general Jørgen Rantzau to capture men from the French advance guard. Many of those troops managed to escape and alerted Lieutenant General Charles-Armand de Gontaut, duc de Biron, who commanded the French vanguard to the presence of Allied troops on the west bank. When de Biron advanced, he was disagreeably surprised by the large number of Allied cavalry already across the river, along with the approaching Allied infantry. Although he was ordered to attack by Vendôme, he hesitated upon seeing the reinforced line of twenty infantry battalions (including the four that had been left to guard the pontoon bridges). Biron's own forces comprised only seven infantry battalions and twenty cavalry squadrons. He had been given reliable advice that cavalry could not negotiate the marshy terrain in the area and decided not to attempt a crossing. At this time, Eugène, along with twenty squadrons of Prussian cavalry, moved across the river and occupied crucial positions. While Biron's troops were manoeuvring, the leading British infantry brigade had arrived, under the command of John Campbell, 2nd Duke of Argyll. Cadogan, given authority from Marlborough, attacked Biron's seven infantry battalions of Swiss mercenaries with his division (consisting mainly of cavalry). The isolated Swiss mercenaries were immediately pushed back and the Allied force destroyed Biron's units, until they reached a large mass of French cavalry, at which point they were forced to retire, outnumbered. The force which performed this action was Rantzau's cavalry, with the future King George II among them.