The movie "Reflections in a Golden Eye" can be viewed as a prequel to "Apocalypse Now". SPOILER ALERT

In RiaGE, Brando plays an Army Major in the early 1950s who is slowly going insane due to his wife's (Elizabeth Taylor) infidelities with a Lt. Colonel played by Brian Keith and his own repressed homosexual urges toward a weird enlisted man played by Robert Forster. At the end, Brando shoots the enlisted man, who has been creeping into his wife's room every night to watch her sleep and to sniff her undergarments. Brando kills the enlisted man not to protect his wife, but out of jealousy because he thought the enlisted man was coming to see him.

I imagine that after the killing, which is assumed to be a justified homicide of an intruder, Brando and his wife are transferred to another post. There, Brando completely buries his homosexuality under a rugged, masculine image, having 'killed' that part of his personality when he shot the enlisted man. He even impregnates his wife, fathering the son he mentioned to Willard in AN.

To prove himself to be a real man, Brando goes through Special Forces training at an advanced age and when the Vietnam War begins, he has made the rank of Colonel. He's even crazier now, though, than he was in the era of RiaGE, and he goes rogue in the jungle and creates his own rebel army, causing the Army to send Willard in to "terminate him with extreme prejudice."

Pictures of Brando in RiaGE were used as photos of a younger Kurtz in his dossier as seen in AN.