December 1943. Sledge and Oswalt stumble through Marine weapons training, learning to fire mortars. Meanwhile, Leckie and his group celebrate Christmas aboard a naval transport ship, bound for combat on Cape Gloucester, New Britain. Once on the island, the men repel a night-time Banzai attack during a torrential downpour. Soon, the jungle itself becomes the primary enemy; the relentless rain, mud and insects begin to wreak havoc on the men's physical and mental health. Leckie confronts his commanding officer when that officer steals his prized Japanese chest and pistol. After being assigned KP duty as punishment, Leckie watches in horror as a fellow Marine meticulously hangs up his uniform in the rain before proceeding to blow his brains out.
In May 1944, the men are shipped to Pavuvu, a rat-infested island, to await orders. Dispirited and suffering from recurring enuresis, Leckie is sent to a hospital on Banika Island for observation. When his razor blades and belt are confiscated, Leckie asks Dr. Grant why he's been placed in the psychiatric ward and begins to question his own sanity. Leckie is shocked to discover that Gibson is also locked up in the ward for trying to steal a plane home, and he sees how easy it would be to slide into madness.
Instead, Leckie asks Dr. Grant to authorise his return to his combat unit as the most important thing to him is to get back to his comrades.