Army Captain Willard is a largely passive character. In fact, Martin Sheen replaced Harvey Keitel in the role after Coppola decided Keitel seemed like too active a screen presence. Sheen brings a more muted presence to the film than the forceful Keitel and, as a result, is more compelling as the audience’s guide into Vietnam. Willard’s primary action is to kill Kurtz. He spends the rest of the film watching intently and internalizing what goes on in the jungle. In his narration, Willard points out the disturbing ironies of war and attempts to insert a faint notion of morality. As he becomes more alert to the absurdities of war and the darkness of human nature, so do we. Nevertheless, we relate to him slowly, despite his role as the film's protagonist, due to his equivocal and impersonal nature. Willard frequently stares off at a point above our shoulder. The war has shell-shocked him, and the film similarly shell-shocks us.
The first shot of Willard inverts his face and superimposes it over the left side of the screen. His eyes are wide open and disturbingly blank. The subsequent scene introduces him as a man who has reached his breaking point. He is in the midst of a nervous breakdown, a state of dementia induced by alcohol and a sense of alienation from the civilized world. When the scene was shot, Sheen actually was drunk and insisted the cameras keep rolling, even after he bloodied his first by accidentally punching the mirror. Thus, from the opening scene Sheen portrays Willard as a man changed irreversibly by war. He managed to leave it physically but could not free his mind. Now he is back, abandoning all ideas of home, resigned to and eager for a return to combat.
Willard’s behavior is at times infuriatingly passive. He takes the mission—“what the hell else was I gonna do?”—and stays out of events that do not affect that mission directly. He interacts with the PBR crew only minimally. He finds Kilgore and goes along with Kilgore’s mass mayhem. He observes the Playmates’ show with amusement, barely participating. Most of Willard’s time on the river is spent reviewing Kurtz’s dossier, understanding and relating to his target more and more. The only action he takes prior to killing Kurtz is his murder of the Vietnamese peasant on the sampan—yet he only takes this action in order to preserve his mission’s priority. Even Willard’s slaughter of Kurtz is arguably passive: not only is Willard following his orders without judgment, he also is doing exactly what Kurtz wants him to do. While it might be argued that Kurtz’s murder is the only action Willard ever takes in Apocalypse Now, an argument also could be made that his only real, self-made decision is to leave Kurtz’s compound and retreat from the darkness it breeds.
Allegorically, Willard’s journey to Kurtz is a metaphor for a journey into the darkness of the soul. His mission is to find and kill Kurtz: ultimately he fulfills his mission, but along the way there is some question as to whether he will kill Kurtz or join him. As Willard increasingly aligns himself with Kurtz, he begins more fully to understand the reasons behind Kurtz’s insanity. This understanding is fueled by his own descent into near madness. But Willard is able, in the end, to retreat from his descent’s endpoint. Does he return to civilization? The film gives no answer. However, it does imply that Willard at least has given himself the opportunity to reenter the civilized world and its framework of morality—and it leaves the choice to do so up to him.