Daniel is a young, disaffected Navy lawyer who has spent his short career seeking the easiest plea deals instead of going to court. He struggles with the legacy of his famous civil rights lawyer father, using a carefree, arrogant demeanor to avoid challenging himself. Assigned to defend two Marines accused of murder, his natural intelligence and slowly awakening sense of duty pull him into a complex legal battle.

Nathan is the intimidating, powerful Colonel who commands the military base at Guantanamo Bay, Cuba. He views the world through a strict dichotomy of good and evil, believing his harsh methods are necessary to protect the United States from its enemies. His intense moral clarity and immense authority make him fiercely defensive of his command and deeply resentful of civilian interference or legal scrutiny.

Joanne is a deeply dedicated, hardworking lawyer working for Internal Affairs in the US Navy. Operating within a heavily patriarchal military institution in the 1980s, she faces constant institutional sexism and must work exceptionally hard to earn respect. She firmly believes that Santiago's death was not a simple murder but part of an illegal hazing ritual, driving her to push for a full investigation and trial.

Sam is Kaffee's hardworking, unflashy legal counterpart and close friend. Unlike the carefree Kaffee, Weinburg is a dedicated family man who handles the necessary, unspectacular groundwork of military law. Although he personally detests the actions of the accused Marines, his deep investment in the legal system compels him to ensure they receive a fair and robust defense.

Harold is a proud, intelligent Marine Corporal fiercely devoted to the military's strict code of honor. As a squad leader, he believes absolutely in the chain of command and prioritizing the unit above individual needs. His unwavering commitment to his training makes him deeply resentful of Kaffee's flippant attitude and highly resistant to accepting any plea deal that would brand him as dishonorable.

Louden is a young, impressionable Marine Private who lacks a strong family background and relies entirely on the Marine Corps for structure and purpose. Less intellectually capable than his peers, he implicitly trusts his superiors and views following orders as his absolute duty. He struggles to comprehend the legal peril he is in, believing that his obedience to command should shield him from punishment.

Matthew is a Marine Captain stationed at Guantanamo Bay under Colonel Jessup's command. Initially committed to the military's rigid ideology, he experiences a severe crisis of conscience following Santiago's death. Recognizing the moral failings of his institution, he becomes increasingly erratic as he seeks to expose the truth about the base's command structure, acting as a crucial but unstable asset to the defense.

William is a young Marine Private stationed at Guantanamo Bay whose tragic death sets the plot in motion. Struggling significantly with the intense physical demands of Marine training, he becomes an outcast within his unit. Desperate to escape his harsh environment, he writes numerous letters begging for a transfer, even offering to expose misconduct on the base to secure his departure.

Jack is the lead military prosecutor assigned to the trial concerning Santiago's death. He is a pragmatic and capable lawyer who initially tries to resolve the case quietly with a plea bargain to spare the Marine Corps from negative publicity. Despite his role as the prosecution, he maintains a professional and occasionally collegial dynamic with Kaffee as the legal proceedings intensify.

Kendrick is a Marine officer stationed at Guantanamo Bay who firmly enforces Colonel Jessup's rigid standards. He expects absolute perfection from his subordinates and holds profound contempt for any Marine who fails to meet the unit's rigorous demands. He is deeply implicated in the chain of command that governs the controversial disciplinary actions taken against struggling soldiers.

Captain Whitaker is a senior legal officer who manages case assignments for the military lawyers. He plays a central role in assembling the defense team, balancing Galloway's intense demands for justice with Kaffee's more relaxed approach to military law.