At the start of his career, he was a protégé of the maréchal de Maillebois, accompanying him on a secret reconnaissance mission to France's Alpine frontier.

Having also worked in secret correspondence with smaller Italian states, he was in 1744 an aide-marechal des logis, which is an assistant to a French chief of staff during the War of the Austrian Succession.

An expert in mountain warfare, military engineering and fortifications, he devised the French invasion of Piedmont that led up to the Battle of Madonna dell'Olmo in 1744.

At the end of 1759, he was made king's chief commissioner and charged with delineating the border between France and Piedmont-Sardinia, a mission concluded by treaty on 24 March 1760.

There is a popular myth that under the direction of the minister of war, Choiseul, in 1764 he established a staff-officer training school at Grenoble (it disappeared in 1771), where he taught on mountain warfare.