Napoleon’s chief of staff in L’Armée du Nord was Marshal Soult, formally Jean-de-Dieu Soult, Duke of Dalmatia. He served as the army’s Major Général during the Waterloo campaign of 1815.
Soult had extensive military experience, having served as a senior commander under Napoleon in several campaigns. Napoleon recalled him during the Hundred Days and appointed him to replace Marshal Louis-Alexandre Berthier’s former staff role. Berthier, who had been Napoleon’s longtime chief of staff, was dead by 1815, making Soult the senior coordinating officer at Waterloo.
Soult’s duties included transmitting Napoleon’s orders, coordinating corps movements and maintaining communications across the army. He was not the same person as Ney, who commanded major forces in the field, or Murat, Napoleon’s famous cavalry commander and former king of Naples. Soult’s staff role was therefore administrative and operational rather than command of a single frontline corps.