I once told a friend (circa 1994) that I'd seen 'Apocalypse Now' about twenty-five times, and I was just about starting to get into it. There's so much - so much - going on that while you can certainly follow the main premise on first viewing, there's no way you'll appreciate everything that's going on. And after about twenty-five viewings I was beginning, just beginning, to get my head around it.
And then in 2001, Francis Ford Coppola went and released a longer version ("Redux"), which added a variety of scenes (most notably the French plantation sequence) but also re-ordered and slightly extended some other scenes - placing the water-ski scene on the river where it SHOULD be (after they begin sailing up the river!), explaining the problem of having napalm in the morning (it kills the surf) and why the boat was hiding under trees when they went looking for mangos (hiding from Kilgore after stealing his surf boards). The whole thing was re-organized, made more sense, added more character and atmosphere... and made us all wish he'd made an even longer version so we could see even more of the cut scenes.
The documentary concerning the making of the film - called 'Hearts of Darkness' after the Joseph Conrad story that inspired the film - shows the craziness, excesses and tensions that went into making the movie itself (in itself it could be described as an epic) and I'd recommend watching that to find out about what really went on, and how we end up with the final versions of the film we have today. But it will suffice to say for now that the scene where Martin Sheen punches and shatters a full-length mirror was a totally unscripted, ad libbed moment of madness.
The first few times you watch the film itself, you don't even need to bother about the Marlon Brando character really - pay attention instead to Martin Sheen's character development, the storyline of what the Generals want from him, the craziness of Kilgore, the psychotic and even psychadelic scenes around the last outpost at the bridge and the deeply aware response to Sheen's question "soldier, do you know who's in charge here?" - response: [pause] yeah.
Then eventually after several watches you get everything else down, all the boat incidents, Dennis Hopper's wonderful photo-journalist, "if I say it's safe to surf this beach, it's safe to surf this beach!"... and finally decide it's time to pay attention to Marlon Brando's Colonel Kurtz. And you just listen to his inane ramblings and ridiculous orders - I still don't see why Chef had to die really - and let the poetry of this self-obsessed, half-crazed nutter in the jungle just wash over you. And frankly I'm probably talking about Brando himself there, not Kurtz - huge swathes of his monologues are totally ad-libbed and just cut with minimal processing to include in the final film.
They all pretty much went nuts making this movie. It's scary but almost documentary in its final form, Brando's voice echoing in the final scene.
The horror. The horror.