In 1947, HUAC began investigating the film industry., Believed that movies were spreading communist propaganda., Called many screenwriters, directors, and actors to testify.
The Hollywood Ten: Ten writers and directors refused to testify, citing the First Amendment (freedom of speech/association). They were charged with contempt of Congress, jailed, and blacklisted from working in the industry. Notable names were Dalton Trumbo, Alvah Bessie, Lester Cole, etc.