Gregoire was drafted on 29 May 1951 to join the IInd Battalion for basic training. As Soldat de 2e Classe, described by his instructors as "clumsy with a lack of energy and initiative," he took an additional course to become a driver for tracked vehicles. During this training, according to his instructors, his attitude changed and he became more attentive and more alert.

On 2 February 1952, he volunteered with the second contingent. Rumour has it that Gregory 'slept' through the Korean campaign. Even during air strikes and heavy artillery fire, he always kept his cool. Thus, he was nicknamed "the slow one". On 27 September 1954, he was officially released from his military obligations. He died on 23 May 1994.