On 13 November 1947, Henri was officially called in for military service where he joined the Ist Battalion for basic training. In October 1948, shortly before his compulsory term was about to end, he was transferred to the Corps de la Garde, from which he was immediately detached to the supply service. On 13 November 1948, he was released from the military.

While fighting as a volunteer among the first contingent in Korea, Henri sustained a combat injury while on patrol, as his left leg was badly wounded by a detonating grenade. However, he did not leave his comrades but continued to follow the orders of his superior officers, for which he received praise from the Colonel and commanding officer in Korea, Albert Crahay. After his return to Luxembourg, he quit the army, later to work for the steel manufacturer ARBED in Rodange and at the Weber wine store in Beggen.