He remained in the army and became a leading supporter of a modern army made up of armoured divisions. Delestraint retired in 1939 but was recalled to the armed services at the beginning of the Second World War and led the counter-attack against the German Army at Abbeville (3rd-4th June, 1940). After France surrendered Delestraint retired to Bourgen Bresse.
Delestraint was recruited to the French Resistance by Henry Frenay. After visiting Charles De Gaulle in London he agreed to head the Armée Secrete. Delestraint returned to France with Jean Moulin on 24th March 1943.
René Hardy, a member of the resistance had been arrested and turned and his information led to Delestraint being arrested by the Gestapo on 9th June, 1943. After being interrogated by Klaus Barbie he was deported to Nazi Germany.