Film scholar Greg Jenkins has analyzed the adaptation of the novel as a screenplay. The novel is in three parts and the film greatly expands the relatively brief first section about the boot camp on Parris Island and essentially discards Part III. This gives the film a twofold structure, telling two largely independent stories that are connected by the same characters. Jenkins said this structure is a development of concepts Kubrick originally discussed in the 1960s, when he talked about wanting to explode the usual conventions of narrative structure.[130]
Sergeant Hartman, who is renamed from the book's Gerheim, has an expanded role in the film. Private Pyle's incompetence is presented as weighing negatively on the rest of the platoon; unlike those in the novel, he is the only under-performing recruit.[131] The film omits Gerheim's disclosure he thinks Pyle might be mentally unstable—a "Section."—to the other troops; instead, Joker questions Pyle's mental state. In contrast, Hartman praises Pyle, saying he is "born again hard." Jenkins says that portraying Hartman as having a warmer social relationship with the troops would have upset the balance of the film, which depends on the spectacle of ordinary soldiers coming to grips with Hartman as a force of nature who embodies a killer culture.[132]
Some scenes in the book were removed from the screenplay or conflated with others. For example, Cowboy's introduction of the "Lusthog Squad" was markedly shortened and supplemented with material from other sections of the book. Although the book's third section was largely omitted, elements from it were inserted into other parts of the film.[133] For instance, the climactic episode with the sniper is a conflation of two sections of Parts II and III of the book. According to Jenkins, the film presents this passage more dramatically but in less gruesome detail than the novel.
The film often has a more tragic tone than the book, which relies on callous humor. In the film, Joker remains a model of humane thinking, as evidenced by his moral struggle in the sniper scene and elsewhere. Joker works to overcome his own meekness rather than compete with other Marines. The film omits Joker's eventual domination over Animal Mother shown in the book.[134]
The film also omits Rafterman's death; according to Jenkins, this allows viewers to reflect on Rafterman's personal growth and speculate on his future growth after the war.[133]
