After working as a volunteer for four years for the mayor of Bernay, Eure, Prioux joined the 6th Dragoon Regiment on 9 August 1897.

Subsequently attending Saint-Cyr military academy, he was commissioned as a second lieutenant in the 6th Chasseurs Regiment on 1 October 1899.

While on orders to report to the 11th Cuirassiers Regiment, he took part in the French military mission to Poland in 1929, of which he became commander in 1931.

The Germans allowed him to return to Vichy France in April 1942,[3] where he was placed in the reserves in May and promoted to the rank of général d'armée in September 1942.

He later served on the staff of General Henri Giraud, and was among those named for ouster by Charles de Gaulle, the leader of the Free French.