Suffren graduated from the Gardes-Marine in 1747 as an ensign, and worked on commissioning the brand new 74-gun "Monarque", under Captain La Bédoyère, in a squadron under Des Herbiers de l'Estenduère. He took part in the Second Battle of Cape Finisterre on 25 October 1747, where La Bédoyère was killed and "Monarque", badly damaged, was captured. Suffren was taken prisoner.