Beginning with boot camp in MCRD Parris Island, South Carolina, the story follows Leckie through basic training and then to New River, North Carolina where he is briefly stationed, and follows him to the Pacific.
Leckie is assigned to the 1st Marine Division and is deployed to Guadalcanal, northern Australia, New Guinea, Cape Gloucester, before being evacuated with wounds from the island of Peleliu. Helmet for My Pillow is told from an enlisted man's point of view; a reprint edition stated the book was about "the booze, the brawling, the loving on 72-hour liberty, the courageous fighting and dying in combat as the U.S. Marines slugged it out, inch by inch, across the Pacific."