Drafted into the army under the Elite Conscription Act, William is a recent physics graduate who initially plans to teach. He holds a deep skepticism of military authority and sees through official propaganda regarding the Tauran war. Despite his pacifist leanings and intellectual background, he is forced to adapt to the brutal, emotionally detached reality of basic training and combat in deep space. He relies on his scientific knowledge and a carefully constructed emotional distance to survive hostile alien environments.

Margay is a biology student drafted into the military alongside Mandella. She acts as a temporary team leader during simulated training but strongly dislikes command positions. Operating as a capable soldier, she expresses deep moral reservations about killing and feels immediate empathy for the alien creatures they encounter. She seeks emotional connection to maintain her humanity while fighting in extreme conditions.

Cortez is a battle-hardened first sergeant who enforces strict discipline upon the new recruits on Charon. He is a career military man who fights directly alongside his troops on the ground. He views the enemy with absolute hatred, encourages his soldiers to abandon their moral reservations, and triggers post-hypnotic suggestions to increase their aggression in combat.

Stott is a decorated veteran and the commanding officer of Mandella's first platoon. Unlike Cortez, he issues orders from a distance and rarely engages in combat alongside the ground troops. He treats recruits as expendable assets, frequently denigrating their performance during debriefings and punishing them heavily for simulated failures.

Richard and April are communal farmers living in South Dakota. They participate in the government's agricultural commune system as a way for Richard to avoid prison for purchasing counterfeit ration tickets. They endure a harsh, labor-intensive life while constantly guarding their property against armed raiders searching for food.

Beth is William Mandella's mother, living in a heavily fortified apartment complex in a crime-ridden, food-rationed future Earth. She adapts to the changing social norms and desperate living conditions with complete pragmatism. She accepts the necessity of hiring bodyguards, installing heavy window bars, and engaging in government-encouraged relationship structures.

Charlie serves as an executive officer and close confidant to Mandella during later deployments. He balances military pragmatism with a clear understanding of troop morale. He acts as a direct advisor who challenges his commander's lenient policies, warning him about potential mutinies and the necessity of strict discipline in combat zones.

Dr. Alsever is the company doctor serving on Mandella's command team. She acts as part of his inner circle, offering practical advice on personnel issues and expressing deep skepticism about the military's extensive genetic engineering programs. She favors decisive, extreme measures to protect unit cohesion when discipline breaks down.

Rogers is a biologist drafted into the platoon alongside Mandella. She engages in the socially mandated sexual relations encouraged by the military and provides initial scientific assessments of the alien environments and indigenous creatures they encounter on missions.

Rhonda is Beth Mandella's roommate in the socially engineered future Earth. She embraces the fluid sexual norms of the new society and explicitly challenges William to abandon his outdated twentieth-century sensibilities regarding gender and relationships.

Hilleboe is an officer serving under Mandella who strongly advocates for traditional chain-of-command discipline. Her hardline approach contrasts with her commanding officer's relaxed command style, creating friction regarding how the platoon should be managed in the field.

Graubard is a deeply aggressive soldier who initiates violent altercations with other recruits. His inability to maintain discipline leads to continuous fighting, forcing his superiors to confront the moral weight of military justice and execution when he attacks the commanding officer.

Captain Siri is a military officer who informs returning units about Earth's dire population and food crises. He explains the military's active encouragement of specific social behaviors designed to manage the societal collapse and resource shortages on Earth.

Colonel Kynock is a temporal orientation officer responsible for updating returning soldiers on centuries of Earth's history. He assesses psychological profiles, noting the tension between an individual's pacifist leanings and their military duty before sending them back into the field.