Kammala jumla mai zuwa: A farkon yaƙe-yaƙe na Napoleon, Marcognet ya kasance babban jami'in da ke jagorantar brigade a cikin Marshal na Faransa Michel Ney. Ya jagoranci sojojinsa a Günzburg, Elchingen, da kuma Scharnitz a 1805. A cikin yaƙin 1806-1807, ya jagoranci tawagarsa a Jena, Magdeburg, Eylau, Guttstadt-Deppen, da Friedland. Bayan da aka tura rundunar Ney zuwa Spain, ya yi yaƙi a
Tamames, Alba de Tormes, Ciudad Rodrigo, Almeida, Bussaco, Torres Vedras, Casal Novo, da kuma Fuentes de Onoro.