Star Trek ? Patterns Of Force (2nd Season, Episode 52)

Episode 52 in the popular 60s science fiction TV series that was aired on 16 February 1968. Investigating the disappearance of a Federation historian John Gill, the Enterprise crew finds out that the missing scientist has turned the planet Ekos into a national socialistic state, similar to Nazi Germany, and that he himself is, in fact, the Fuhrer.