'It was no accident...'
This statement and the fact that most of the voiceover is in the past
tense indicates that the events of Apocalypse Now are illustrative of
Willard's recollections. This sets the tone for the film, because
Coppola gives his audience the expectation of a transformative
journey, but also, we know that Willard is going to survive and Kurtz
is going to die. By calling himself the 'caretaker of Kurtz's memory,'
Willard foreshadows the decision he makes at the end of the film. When
Willard first arrives at Kurtz's compound, it seems as though Kurtz
only keeps Willard alive because he wants to give him all the
knowledge and guilt so he can take Kurtz's place. Once Kurtz has
accepted that his time has come, he entrusts Willard with a mission
that will take him back out of the jungle. Kurtz wants Willard to
share his story, all of it, with his own son. Therefore, even though
Kurtz deserves to perish for all his moral violations, Willard
understands why he snapped, and can hopefully, use Kurtz's story to
prevent another Vietnam.
'Never get off the boat...'
Willard wonders what Kurtz saw during his first tour that sent him in
such a radical direction (which resulted in his splitting 'from the
whole fucking programme'.)
and finally, from an 'A level film Studies - Focus Film Factsheet...
He is a man who has fought so much he has forgotten why he is
fighting; all he knows is that he fights. As a representation of a
dehumanised soldier the performance is electrifying. His last
voice-over monologue (02:57:48) suggests that despite having killed
Kurtz, Willard will remain as conflicted and alienated as ever: ‘They
were going to make me a Major for this and I wasn’t even in their
fucking army anymore’.
1.Gradesaver AN Study Guide
2.A level Film Studies - Focus Film Factsheet
I have some of my own thoughts as well but cannot verify them using any other source. It's a complex film and much of this content is still subjective analysis so do not take it as the be all and end all.