Included in Colonel Kurtz's jungle 'library' was James Frazier's, "Golden Bough".  In it, Frazier made the claim that all pre-Christian religions were fertility cults that revolved around the worship and periodic sacrifice of a sacred king, who was also the incarnation of a dying and reviving god, who died at the harvest and was reincarnated in the spring.  Francis Ford Coppola would use Frazier's theory of the king's sacrificial death when formulating the ending of "Apocalypse Now", which was initially inspired by the Ifugao animal sacrifice.  He decided that Kurtz would be killed.  But not by way of an airstrike, which was considered to the point that such a scene was actually made.  No.  Kurtz would be sacrificed, just like some kind of sacred king.