He served as a junior officer in the War of the Spanish Succession and as brigadier in the campaign of 1734 on the Rhine and Moselle, where he won the grade of "Maréchal de camp". He was employed under his brother in political missions in Bavaria and in Swabia in 1741–1742, became a lieutenant-general, fought in Bohemia, Bavaria and the Rhine countries in 1742–1743, and was arrested and sent to England with the marshal in 1744. On his release he was given a command in the Army of Piedmont, and troops under his command reinforced the beleaguered city of Antibes during the 1746-7 siege, preventing its fall to the Austrians. Belle-Isle ultimately was killed at the Battle of Assietta on 19 July 1747.