Andrew is a six-year-old child prodigy recruited by the International Fleet for Battle School. As a "Third" child in a society with strict population limits, his existence is a constant source of tension for his parents. He possesses extraordinary intelligence and strategic intuition but deeply fears his own capacity for violence. He seeks only to be left alone yet repeatedly finds himself forced to defend himself against aggressive peers.

Peter is a brilliant, ruthless older brother who was rejected from Battle School for his cruel tendencies. He masks his sociopathic desire for control behind an increasingly amiable public facade. Highly ambitious, he manipulates those around him and harbors grand political aspirations on Earth.

Valentine is known for her exceptional empathy and intelligence. The military deemed her too mild-mannered for Battle School, leaving her at home on Earth. She serves as the primary protector of her younger brother and is the only person he completely trusts.

Graff is the head of Battle School and an officer in the International Fleet. He views his extreme methods as entirely justified by the need to save humanity from alien threats. He intentionally isolates his most promising student to forge an independent, unbeatable military commander.

Bernard is a new Battle School recruit with a French accent who immediately targets smaller children. He gathers followers through intimidation and mockery, establishing himself as a primary bully in his launch group. He holds long-standing grudges when humiliated.

Alai is a smart, pragmatic Battle School student who adapts quickly to zero gravity. He serves as a social bridge between rival factions in the launch group, showing both a natural gift for connection and a shrewd understanding of military strategy.

Petra is one of the few girls at Battle School and a highly talented sharpshooter. She possesses a fierce, independent streak and often ignores the unwritten social rules of the school, choosing instead to help outsiders improve their skills.

Bonzo is the fiercely proud commander of Salamander Army. Driven by an intense adherence to a personal code of Spanish honor, he cannot tolerate looking weak or foolish. He strictly enforces his authority, often sacrificing sound military strategy to maintain absolute control over his subordinates.

Dink is a highly capable toon leader who repeatedly refuses promotions to commander. He harbors a deep cynicism toward the teachers and the school's systems, believing the adults use the games merely to manipulate the children. He prefers the simple joy of zero-gravity movement over political power.

Bean is an exceptionally small, brilliant, and cocky young boy who enters Battle School late in the training cycle. He learns rapidly, asks sharp questions, and actively petitions for leadership responsibilities despite his youth and inexperience.

Mazer is a legendary military figure credited with stopping the previous alien invasion decades ago. He functions as a highly demanding, secretive instructor who pushes his pupil to the absolute limits of physical and mental endurance. He adopts the tactics of the alien enemy to prepare his student for war.

A compliant citizen who hides her Mormon background to assimilate into a strict society. She deeply loves her children but feels the crushing societal weight of having borne a third child in an overpopulated world.

A man who renounced his Catholic faith to conform to population laws. He attempts to raise his highly intelligent children under the watchful eye of the government, carrying quiet shame over their family size while taking pride in his civilian political access.

A schoolyard bully on Earth who targets weaker children. He relies on his gang of friends to intimidate others, lacking the strategic foresight to handle a victim who fights back aggressively.

A teacher and military officer at Battle School. He manages the battle scenarios and is sometimes skeptical of the extreme, rule-breaking measures taken to accelerate training, though he consistently complies with his orders.

An older boy assigned to supervise the new recruits upon their arrival at Battle School. He introduces himself as the group's "mom," balancing genuine concern for their well-being with a strict, no-nonsense approach to discipline.

A new recruit in the launch group who becomes an easy target for bullies due to his distinctive walking style. He quickly aligns himself with anyone willing to undermine his tormentors.

The chaotic commander of Rat Army. He runs a disorganized barracks and relies heavily on his independent toon leaders to maintain the army's high rankings, often acting out of spite when he feels slighted by new recruits.

The commander of Rabbit Army. Unlike his peers, he accepts defeat with dignity and maintains a respectful demeanor, recognizing superior strategy rather than holding a petty grudge.

The leader of the alien species currently at war with humanity. She communicates telepathically and tries to understand the humans who fight her kind. She reaches out to the enemy by constructing familiar environments from human memories.