During the Napoleonic Wars Maucune led the 39th in Marshal Michel Ney's VI Corps at Elchingen in the 1805 campaign and at Jena, Magdeburg, Soldau, and Eylau in the 1806–1807 campaign. Promoted to general officer, he led a brigade at Friedland in 1807. In Spain from 1808 and 1811, he commanded a brigade at Gallegos, Tamames, Alba de Tormes, Ciudad Rodrigo, Almeida, Bussaco, Casal Novo, and Fuentes de Onoro.