In September 1919, Thierry d'Argenlieu left the navy and entered the Carmelite Order as P?re Louis de la Trinité (Father Louis of the Trinity). In February 1932, he became provincial superior in Paris. In 1939, he was called back into the navy at Cherbourg, and in February 1940, he was appointed captain. Captured by the Germans on 19 June, Thierry d'Argenlieu escaped three days later and joined General Charles de Gaulle's Free French movement in Britain by the end of the month. Thierry d'Argenlieu participated in the ill-fated September 1940 Free French attack on Vichy forces at Dakar and was wounded three times. He then took command of Free French naval forces in Equatorial Africa. Operating in conjunction with Colonel Philippe Leclerc on land, he led the naval operations at Gabon.
Between February and May 1941, Thierry d'Argenlieu led a mission to Canada seeking to rally support for de Gaulle, and by July, he was named high commissioner for the Pacific, which involved, in conjunction with the other Allies, defending French territories in the Pacific and easing diplomatic tensions between Free French administrators in Tahiti and New Caledonia. The following year, in May, he helped rally the Wallis and Futuna Islands.
In June 1943, Thierry d'Argenlieu was promoted to rear admiral and became commander in chief of all Free French naval forces. Following the liberation of France, he was advanced to vice admiral in December 1944 and made "chef d'état major general adjoint de la marine." He had been named a "compagnon de la libération" on 29 January 1941, when he also became the first grand chancellor of that order, serving until 1958.
After the war, the French government sent Thierry d'Argenlieu to San Francisco in April 1945 as a delegate to the UN meetings and then to Indochina as high commissioner to reestablish French control there. His efforts to roll back the colonial clock and his decision to employ force and order the shelling of Haiphong by the cruiser Suffren on 23 November 1946 led directly to the outbreak of the First Indo-China War.
In June 1946, Thierry d'Argenlieu was promoted to admiral. The following year, he was recalled to Paris, and in 1948, he returned to his monastery in Brest. He died in Relecq-Kerhuon (Finist?re), France, on 7 September 1964.
Alford, Élisée. Le Père Louis de la Trinité, Amiral Thierry d'Argenlieu. Paris: Desclée, De Brouwer, 1969.; Auphan, Gabriel Adrian Joseph Paul, and Jacques Mordal. The French Navy in World War II. Trans. A. C. J. Abalot. Annapolis, MD: Naval Institute Press, 1959.; Thierry d'Argenlieu, Georges. Souvenirs de guerre, juin 1940—janvier 1941. Paris: Plon, 1973.