Lee started to study for an art degree but returned to Spain in 1937 as an International Brigade volunteer. His service in the Brigade was cut short by his epilepsy. These experiences were recounted in "A Moment of War" (1991), an austere memoir of his time as a volunteer in the Spanish Civil War (1936–39). According to many biographical sources, Lee fought in the Republican army against Franco's Nationalists. After his death there were claims that Lee's involvement in the war was a fantasy; the claims were dismissed as "ludicrous" by his widow.