By 1691 von Hompesch was a major in the Dutch Horse Guards, becoming Colonel of that regiment in 1711. On 6 July 1698, he was appointed to the English court position of Master of the Privy Buckhounds under William III of England. In 1701 he was appointed major general. During the war of the Spanish Succession War he fought at the Battle of Ekeren (1703), and in the following year in the rank of Lieutenant General at the Battle of Blenheim, where he commanded the second line of cavalry. Thereafter Marlborough appointed him and Major General Jacques-Louis, comte de Noyelles en Falais (who had commanded a cavalry brigade at Blenheim) to command of the Trier area. Von Hompesch fortified Trier and occupied Saarbrücken.