Simonet left the United Kingdom on 29 August 1940 for an expeditionary force in Dakar which sought to rally French West Africa in favor of Free France. He fought in the Battle of Dakar, which attempted to free the key port from Vichy France. He was then stationed in Cameroon in French Equatorial Africa, where he continued his training until January 1941. He took part in the Syria–Lebanon campaign in June and July 1941, the result of which was decided in Damascus as a victory for Free France. Simonet served in the 1st Free French Brigade under General Marie-Pierre Kœnig and participated in the North African campaign from January to July 1942. Fighting in a Jock column on 16 March, he faced a strong attack by enemy tanks. However, he did not abandon his position and saved a large amount of French military equipment. He also fought in the Battle of Bir Hakeim from 26 May to 21 June, serving as a telephone operator until 10 June before taking up arms and aiding a boost in Free French morale with a victory.