As a Free French, Alain de Boissieu was involved in several the military operations over Bayonne (Easter 1942) and Dieppe (Dieppe Raid, August 1942), in Madagascar and Djibouti with the FFL. He fought in the Battle of Normandy from 30 July 1944, as an officer of the famous 2nd Armored Division () under General Philippe Leclerc de Hauteclocque, and was wounded on 12 August. He fought for the Liberation of Paris (25 August 1944).