"I knew in the making of Empire that this was to be the second of a trilogy. Therefore I considered it the second act, the second movement—but it wouldn’t have the same climax that an ordinary film would have, where it sets up a premise, moves along, there is a payoff with a grand climax of some kind of action. The action in this film came at the beginning because it is a continuation of the first film."
January 1, 1970
https://en.wikiquote.org/wiki/The_Empire_Strikes_Back