Just Keep Writing
During the writing stage for Apocalypse Now, Francis Ford Coppola told Milius to “write every scene you ever wanted to go into the movie.” He basically told the screenwriter to put absolutely everything down on paper, no matter what. This led to Milius writing a grand total of ten drafts, with more than 1,000 pages of content in total.
Even though his story differed greatly from Heart of Darkness, he decided to maintain several elements, including the psychotic character of Kurtz and even some of the lines of dialogue. For example, the original novella has Kurtz saying “Exterminate all the brutes!” which also appears in the film as “Exterminate them all!” Kurtz’s final words, “The horror! The horror!” are also taken directly from the book.