 He was then promoted to Lieutenant-Colonel in 1905 and served during the French occupation of Senegal from 1906 to 1908 under General Audéoud.In 1910 he published "La force noire", where he called for the use of French Colonial Forces in the event of a European war.During the First World War Mangin rose from divisional command to that of the Tenth Army for the Second Battle of the Marne, commanding both French and American troops.