Barjot joined the Navy in 1918, and was commissioned as a ship-of-the-line Second Ensign on 1 October 1919, while serving in the harbor of Toulon.

From January 1, 1921, he served aboard the ship Aldebaran of the Pacific Squadron, and was promoted to Ensign on 1 October.

[1] In 1940, at the early stages of World War II, he served in the Anglo-Saxon Department of the French Admiralty.

On 17 November 1940, after the Second Armistice at Compiègne, he was given the rank of commander and posted to Marseille, where he oversaw the local merchant fleet.

There, he assisted the Allied forces in the preparation of Operation Torch; he was one of those present in the Cherchell conference.

Afterwards, he was the marine prefect of Toulon, an office he held until October 1958, when he was transferred to the post of Naval Adjutant to the Supreme Allied Commander in Europe, General Lauris Norstad.