Sgt. Zack, a hard-bitten U.S. Army Infantryman battling Communist North Koreans in the Korean War, is the sole survivor of an enemy attack on his regiment. A bullet hole in Zack's helmet serves as a grim reminder that he narrowly escaped death. When the sergeant regains consciousness, he finds a young Korean boy with an M-1 rifle surveying the scene of the massacre. The boy, an orphan from South Korea, whom Zack names "Short Round," wants to be Zack's friend and insists on scouting for him on his search for the enemy lines. Zack is reluctant to let the boy travel with him, but consents to the arrangement until he can deliver Short Round to safety. On their dangerous journey through the war-torn territory, Zack and Short Round come under attack from two Communist guerrilla soldiers disguised as women praying at a religious site. After killing the two guerrillas, Zack and his charge encounter Corp. Thompson, a black medic who is also the sole survivor of a North Korean attack on his platoon. Thompson joins Zack and Short Round and the three continue their search for the front lines. They eventually encounter an American patrol regiment under the command of Lt. Driscoll, whom Zack knows and dislikes. As Driscoll is in need of an experienced soldier to help his patrol set up an observation post at the front, he offers to put aside his differences with Zack and asks him to join his regiment. Zack initially refuses to join the patrol but changes his mind following a sniper attack by Communist guerrillas. Zack continues, however, to hold his opinion that the men in Driscoll's unit are mere amateurs, especially Priv. Baldy, who carries a music box with him, and Priv. Bronte, a conscientious objector in World War II. Soon after Driscoll's unit and Zack's companions set up their observation post at an apparently deserted Buddhist temple, they come under a surprise guerrilla attack. In the ensuing battle, a Communist officer from Manchuria is taken prisoner by Driscoll, who intends to deliver his prized capture to his base. During his captivity at the observation post, the Manchurian officer tells Driscoll's Japanese-American sergeant, Tankaka, that he should be ashamed of his allegiance to a country that interned his people during World War II. Tankaka ignores the prisoner's words, prompting the prisoner to call him a "dirty Jap rat." While Driscoll's unit prepares to clear out of the observation post and return to camp, they are attacked by snipers and Short Round is killed. Motivated by a desire to avenge the boy's death, Zack kills the Manchurian officer in cold blood. The situation looks bad for the Americans, as a large Communist force is making its way to the temple, but they are saved by the arrival of a U.S. Infantry platoon. In the ensuing battle, however, Driscoll is killed and Zack is injured. Following the defeat of the Communists in the battle, the Infantry division escorts Zack, Thompson and the remaining men in Driscoll's unit back to camp.