In 1940 he undertook several ground engagements in France, and was also involved in the Narvik Campaign. Prior to the Fall of France, Voisin was ordered to evacuate to England. He and a small contingent of men crossed the English Channel from Cherbourg in a daring boat journey lasting several days. Once in England, Voisin met with Admiral Thierry d'Argenlieu and was made Secretary Attaché to Admiral Émile Muselier, leader of the Free French Naval Forces.