On 4 July 1947, Gilbert was conscripted into the Army. Discharged in 1948, he retook his former job as a carpenter. In 1950, he joined the first contingent of volunteers for Korea. After their mission had ended, Gilbert reenlisted with 6 fellow members of the first contingent for a second term.

On 6 September 1952, he was wounded by a splinter of a detonating shell. Even though he initially ignored his injury and continued the fight, he had to be hospitalised one month later. Eager for action, Gilbert rejoined his unit before his official medical discharge, which earned him praising words from his commanding officer. A photo album of unique pictures bears not only witness of his time in service, but let us assume as well that he was one of the very few to bring his own camera to the battlefield.

Having served a total of 616 days abroad as well as having sailed and flown halfway around the world twice, Gilbert left the Army only days after his arrival at the Luxembourg City airport with the second contingent. He took up his former job at the Alphonse Erpelding carpentry, where he had begun his apprenticeship at the age of 14. He continued to work there until his retirement.