After the fall of France in World War II (1939–45), he voted in favour of granting Marshal Pétain the constitutional powers he had requested.

He studied at the Lycée Janson-de-Sailly, and then obtained a diploma from the École des Hautes Etudes Commerciales.

[3] Guy de Wendel was made a captain in May 1918, and commanded a battalion in the last major operations of the war.

[1] Guy de Wendel was also a director of the Beeringen Coal Company and the Orange-Nassau mines.

[5] He was elected deputy of the Moselle on 16 November 1919 on the Lorraine Republican Democratic Union platform, and was reelected on 11 May 1924.

He made proposals for legislation for canalizing the Moselle from Metz to downstream of Thionville, and for making unused barracks and government buildings available for the gendarmerie.

[3] After the outbreak of World War II Guy de Wendel rejoined the army under General Henri Giraud.

On 10 July 1940, in Vichy, he voted in favour of granting Marshal Philippe Pétain the constituent powers he had requested.