As many times as I have seen The Godfather, Part II I have never understood a couple of things about Fredo.
At the New Year's Eve party, an hour or so before Michael lets Fredo know that he knows about his betrayal of him to Roth, Fredo slips away, giving a lame excuse that he "needs a real drink". Not long after, Cuban police show up in Roth's room and kill Michael's henchman before he can kill Roth.
I figure this means that Fredo really went to tell Roth's people about Michael's attempt to assassinate Roth. How else would the police coincidentally all of a sudden know that they needed to get to Roth's room? But why would Fredo do this? At the time, he didn't yet know that Michael was gunning for him.
I've never understood this point and I've never seen it discussed anywhere. Your help is appreciated.
The idea that the Cuban police discovered the plot accidentally, as they were merely on their way to Roth's room to rescue him from the ensuing revolution, has merit. But I would point out a couple of things. First, it is never specifically stated in the movie or in any alternative scripts that I have ever heard of. Second, Fredo's behavior at this point still needs explaining. It's pretty clear that he isn't just going to look for a "real drink". Third, as many times as I have seen this scene, I have never detected any surprise on the face of the Cuban commandant. To all appearances, he seems to know exactly what he will find in Roth's room and he is completely ready for it.
If the Cuban police did, indeed, discover all this by accident, if that is the answer to the question, I will show some real temerity and say that this was one of the few missteps Coppola and Puzo made in the script and in the directing of the movie.