 After having served in the Army, he was appointed in 1756 ambassador in Vienna to Emperor Francis I and Queen Maria Theresa of Hungary.In 1761, he was plenipotentiary to the Augsburg Convention.From 13 October 1761 to 8 April 1766, he served as Secretary of State (minister) for Foreign Affairs, replacing in this office his cousin Étienne de Choiseul (who became in 1763 Secretary of State for War and for Navy).