After the Tours Congress of 1920, Fouchard left the Socialists and joined the French Communist Party.
He asked to be allowed to rejoin the French Army and became one of the leading members in the new Union populaire française.
He moved to the Lot department in Vichy France where he became involved with the French Resistance in the left-wing, Communist-dominated FTP (Francs-Tireurs et Partisans).
Fouchard was arrested by the Vichy government in August 1942 and spent the remainder of the occupation imprisoned, first at Cahors and then at Saint-Sulpice-la-Pointe.
Freed at the liberation of France in 1944, Fouchard served in the reconstituted French National Assembly but did not seek election in 1945.