“The Green Berets” had its cheesy moments (I never saw pine trees in Vietnam) but John Wayne was believable as an Army colonel & had played that role more than once.
But the Duke as a German sea captain or as Genghis Khan was waaaay out of character. He was never good at foreign accents and the makeup job to give him Mongol eyes royally sucked.
But the Duke as Genghis Khan ...Goof grief I forgot about that one. The writing and story was at least pretty good though.