Henri de Groux, The Assault, VerdunAn eerie portrayal by Belgian artist Henri de Groux (1867–1930) of French troops moving forward in a thick haze of smoke and perhaps clouds of diphosgene, a poisonous gas first used by the Germans at Verdun on June 22, 1916. (Musées des Deux Guerres Mondiales, Paris, France/The Bridgeman Art Library)