Richie Perry enlists in the Army at 17. He is sent to a base for training and injures his knee playing on the base's basketball team. As a result, the doctors give him a "medical profile" that declares he is not physically fit to serve in the infantry. However, his profile is delayed in processing, and he is sent to the front lines. Perry's squad becomes his family as they help each other through the most difficult things they have ever faced. Members of their squad die, they witness atrocities, and they struggle to process the aftermath. Perry writes letters home in an effort to understand the war and his role in it, but he is unable to reconcile his belief about the purpose of the war with the day-to-day horrors. He is injured once and returns to his squad with a Purple Heart. When he is injured a second time, along with Monaco and Peewee, the doctors locate Perry's medical profile and send him home.
Peewee is the nickname preferred by Private Gates, who is a clown who says outrageous things to get a reaction from others. He becomes close with Perry on the plane to Vietnam, and the two protect each other throughout their time there. Peewee is a steadfast soldier who backs up Perry on numerous occasions and who is always ready to take on an adventure. Peewee wants to try the wine he finds in a hut, experiment with the salves he acquires from a Vietnamese family, and—if given the opportunity—have sex with a foreign woman. Peewee views his service as an opportunity to explore the world that he will likely never have again. He comes from a poor background and joined the army for the economic opportunity it offered him, but he knows he is unlikely to have another chance to travel the world. Peewee wants to believe that they are in Vietnam for the right reasons, and he is hopeful that he can do some good there. However, he is increasingly aware of how challenging that goal is and frustrated by the fact that life is passing him by, as at home his girlfriend moves on and marries another man.
Monaco is a soldier who enjoys being out in the front of the unit when they are on patrol. He enjoys the role of spotting danger for the squad. Monaco gets along well with all the members of the squad and becomes close friends with Perry and Peewee. Monaco looks forward to returning home, where his girlfriend is waiting for him. While he is in Vietnam, Monaco's girlfriend proposes marriage to him, and he asks the other soldiers to take a vote about whether he should marry her. The squad votes that he should, and Monaco declares that he will schedule the wedding for a date after everyone from the squad comes home from Vietnam. Monaco is injured at the same time that Perry and Peewee are injured. He is pinned down under enemy fire and thinks that he has no way out, but he survives thanks to Perry and Peewee. He physically recovers, but Perry worries that Monaco has not psychologically recovered from his near-death experience by the time they send Monaco back to rejoin the squad.
Johnson is strong and loyal, commanding the respect of all the men on the team. When they first arrive, many of the men are simply intimidated by his size and strength, but over time they come to see Johnson as a trusted authority. Johnson seems to always be aware of what is happening, and he frequently stands up for the other African American soldiers on the squad when they are being threatened or harassed. Johnson does not speak much, and Perry and others do not often learn what he thinks or feels. When he does share thoughts with Perry, he makes astute, clear observations but tells Perry that he will leave the deep, abstract problems for others to puzzle out.
Lieutenant Carroll is a kind man who cares about each of the soldiers under his supervision. He makes an effort to mark each of the deaths with a prayer about angel warriors, bringing a ritual and an honor to their passing. The men trust Lieutenant Carroll implicitly and appreciate his clear and well-considered orders. When he dies, they are shocked and saddened by his loss. Perry honors his memory with a careful letter to Mrs. Carroll, with whom Lieutenant Carroll had dreamed of owning a bookstore.
Sergeant Simpson is an excellent leader who earns the respect of his troops by caring for their lives and working to ensure their survival. Sergeant Simpson is counting the days remaining on his tour by the time that Perry and Peewee arrive, and he is simply trying to survive until he can return home. He feels a strong sense of duty and responsibility for the men under his command, and this enables Captain Stewart to convince Sergeant Simpson to extend his tour by 30 days. Sergeant Simpson manages to survive his tour as well as the additional 30 days, and he goes home safely.
Lieutenant Gearhart is not trained to become the replacement for Lieutenant Carroll, but he is assigned the position because the army has a shortage of officers to fill the post. Lieutenant Gearhart's training in long-range surveillance does not prepare him to lead the squad in an ambush, and his lack of preparation shows when he makes a critical mistake that gets a soldier killed. Lieutenant Gearhart feels responsible and wants to take the blame for the soldier's death, but Perry convinces him that it would make the soldier's family feel worse. Despite a rocky start with the squad, Lieutenant Gearhart redeems himself on the next mission, in which he saves the whole squad. The men come to respect him over time, but they do not feel the kind of bond that they felt with Lieutenant Carroll.