Son of the doctor Alice L. Cobb and the artist Arthur M. Cobb, Humphrey, who had spent his childhood in a boarding school in England and was later expelled from an American high school (he never got to graduate), decided to enlist in the army Canadian at seventeen. After serving in the army during the First World War, he returned to the United States to work in the merchant marine stock trade and in the War Information Office (precursor of the OSS and predecessor of the CIA), devoted mainly to writing propaganda abroad. His novels include Senderos de gloria (1935), later taken to the cinema by Stanley Kubrick, and Todos were valientes (1938). He was also the main screenwriter of the film San Quentin (1937), starring Humphrey Bogart.