Sidney Ellwood is a 17-year-old student at Preshute boarding school. He is deeply influenced by classical literature and poetry, initially viewing war through a romanticized lens of honor and glory. He harbors repressed romantic feelings for Gaunt, surviving the strict anti-gay bias of his 1914 English society by keeping his deepest attachments hidden behind casual physical flings.

Henry Gaunt is an imposing, broad-shouldered student at Preshute who frequently defends others from bullies. As a half-German English youth, he faces severe social pressure to prove his loyalty to Britain, enlisting on his 18th birthday despite his pacifist sentiments. He struggles with his unspoken love for Ellwood and an intense fear of persecution in a deeply homophobic society.

Burgoyne is a former Preshute student who used to torment Ellwood. Stationed as a strategist away from the frontline violence, he wields his authority with vindictive disgust, particularly when he discovers the intimate nature of Gaunt and Ellwood's relationship.

Gideon Devi is an irrepressibly optimistic young man who originally attended primary school with Gaunt before they were separated. He tirelessly plots escape attempts. He brings a lighthearted, non-judgmental approach to life, offering rare and vital acceptance to his friends.

Maud is Henry Gaunt's twin sister. Feeling helpless while remaining at school during the outbreak of conflict, she decides to secretly train as a nurse to contribute to the war effort. She is highly perceptive and holds progressive views on love that contrast sharply with the rigid expectations of her parents.

Maitland is an older student from Preshute who serves as a Captain in the army. He is protective of his younger schoolmates on the front lines and acutely aware of the dangers associated with writing compromising personal letters in a military setting.

Sandys is an older student at Preshute who struggles intensely with the need to hide his sexuality. He uses aggression to mask his physical encounters but eventually confides his genuine romantic feelings for another boy, illustrating the deep psychological toll of societal bigotry.

Hayes is an officer who fights alongside Gaunt and Ellwood. Lacking the wealth and elite boarding school background of the other officers, he occasionally feels out of place but proves to be a loyal, grounded presence amidst the relentless psychological strain of trench warfare.

Archie Pritchard is the older brother of one of Ellwood and Gaunt's friends. He is a placid and comforting presence whose steady loyalty makes him a vital source of emotional support for his friends under extreme duress.

Roseveare is a compassionate classmate at Preshute who understands the unspoken bonds between the boys. He manages the grief of losing peers while trying to support his friends, acting as a grounded confidant throughout their wartime transitions.

Lukas Hohenheimer is a German soldier and medic who cares for wounded enemies. He discovers Gaunt's German heritage and ensures he receives proper medical treatment, representing the shared humanity that persists across enemy lines.

Ernst is Gaunt's cousin fighting for the German army. His perspective on the battlefield highlights the mechanical slaughter of the conflict and the surreal horror of fighting against his own family's country of residence.

Oliver MacCorkindale is a British prisoner of war. He is pragmatic and quick to assess how new arrivals, particularly bilingual ones like Gaunt, can assist in their ongoing tunneling efforts.

Lüneburg is a German officer guarding the prisoner camp. He forms an unlikely camaraderie with Gaunt due to their shared language, demonstrating the complex, humanizing relationships that form despite wartime divisions.

Elisabeth is a German secretary who holds access to crucial identification papers. She is beautiful and becomes the target of a strategic seduction, helping a conflicted soldier realize profound truths about his own identity.

Mr. Roseveare is a British diplomat and the father of a Preshute student. He exemplifies the civilian romanticization of the conflict, speaking proudly of wartime bravery and sacrifice while remaining ignorant of the gruesome realities the young men actually face.