A lieutenant in the Walloon Guards, du Mont fought for the Spanish in many battles during the War of Spanish Succession, distinguishing himself in the Battle of Villaviciosa, and he also took part in the Spanish expedition to Oran (1732). du Mont is best known for his role in the War of the Austrian Succession (1740–1748), a.k.a. King George's War in North America, and incorporating the War of Jenkins' Ear between Great-Britain and Spain.