Augustin Dubail was born in Belfort on April 15, 1851. He graduated from the military school of Saint-Cyr in 1870 and was commissioned an officer in the infantry. During the Franco-Prussian War Dubail fought at Saarbrücken, Spicheren, Borny before being captured at Metz. After the war Dubail served as a professor at Saint-Cyr, as an officer on the border and in Algeria, where in 1901 he became colonel of the 3rd Zouaves.