Haakon Chevalier was a professor of French literature at the University of California, Berkeley. He was a close friend of J. Robert Oppenheimer. He was politically active at Berkeley, joining the Teachers' Union and the ACLU. He was very left-wing and may have been a member of the Communist Party.
In early 1943, Chevalier told Oppenheimer that he knew of a way to pass information to the Soviets. Oppenheimer rejected Chevalier’s offer, but did not report the exchange for eight months. The Chevalier offer, and Oppenheimer's belated reporting of it, were dredged up and used against him in 1954 at the hearing that revoked his security clearance. For more information, see Oppenheimer Security Hearing.
Because of his political leanings, Chevalier lost his job at Berkeley in 1950. He was unable to find another professorship in the United States and moved to France. He died in 1985 in Paris.