After war was declared against Germany in September 1939, both FCM 36 battalions were combined, together with 3e BCC, a R 35 unit, into the 503e Groupement de Bataillons de Chars, the armour reserve of the Second Army.
Following Germany's declaration of war in September 1939, two FCM 36 battalions were combined with 3e BCC, a R 35 unit, to form the 503e Groupement de Bataillons de Chars, the armored reserve of the Second Army.