Muhammad Ali and Joe Louis seldom had a good word for each other–“Slow Joe Louis” was one of the nicer things Ali called his predecessor—and it wasn’t just joking. Louis picked Sonny Liston to win both Ali-Liston fights, and Ali never really forgave him. Louis seemed to be jealous of the brash younger fighter who was set to eclipse him.

This 1966 clip captures the two heavyweight egos when the men were actually working together briefly, with Louis acting in an adviser capacity. But Ali’s stance on the Vietnam war, among other issues, soon led to a bitter falling out.