Karl Marlantes, the author of the book Matterhorn, began work on the novel in 1970, but the book was not published until 2010. While this is a work of fiction, Marlantes himself served in Vietnam during the war, so this story is constructed with his experiences in mind. The protagonist of the story is Waino Mellas, a second lieutenant in the US Marines and a member of Bravo Company.

The setting is the jungle in Vietnam in 1969, near the border of Laos and the demilitarized zone (DMZ). Bravo Company is ordered to summit a steep hill they nickname "Matterhorn" to construct a base to hold off enemy troops. The hill—which is really a small mountain—has impossible terrain, making this project extremely taxing and difficult; the physical and psychological toll on the men is immense. After they have finally erected the fortress, their superiors command them to withdraw and report to another location in the jungle.

Mellas and other members of his company do as they are told and disperse into the jungle. On their way to their new assigned post, the marines encounter every manner of trouble. Marlantes skillfully depicts how taxing these long slogs through the unforgiving maze of jungle, mist, and unfamiliar terrain are on the men. Due to the fog and the density of the landscape, the soldiers realize that they cannot count on US Marine helicopters for support or supplies. In other words, they are completely on their own. When they finally do encounter the North Vietnamese Army (NVA) and suffer casualties, they are forced to carry wounded and dead soldiers on their backs. Because they are so deeply entrenched, once they use up their meager supplies of food and water, the soldiers are forced to go without either for days. They are also low on ammunition, which causes great consternation among the men. In addition to the platoon members who are dispatched by the NVA, one soldier dies from malaria, while another is mauled to death by a tiger. The marines must also contend with leeches and unrelenting humidity.

Once the remaining soldiers are reunited with the rest of their troop, they have a very limited time in which to rest before being ordered back into the fray. When this occurs, the soldiers are dismayed to learn that the NVA members have taken over Matterhorn and that it is now in enemy hands. The marines are ordered to fight the enemy to regain the base at Matterhorn—a base which they themselves built.

When we first meet Mellas, he has just graduated from an Ivy League college and plans to continue his schooling after the war. Mellas is an ambitious young man who dreams of a future in law or politics. He is very concerned about his image and wants to be taken seriously. However, after about a month in Vietnam, Mellas begins to grasp how complicated the war is and how vulnerable and young he is. He does not feel prepared to be in charge of his platoon, which consists of men only slightly younger than he is.

When the men are forced into combat again, they are attacked with mortars and sustain a number of casualties. Once again, the fog will not allow helicopters to land in order to provide support for the wounded or resupply the men with water and food. As more men are wounded, the soldiers are faced with an impossible decision: they must deny some of the wounded care in order to save the men who are not as badly injured. At this point, Mellas dreams of running...