Jacob is a 93-year-old World War II veteran who serves as the beloved great-grandfather to Trevor. As a 17-year-old soldier in 1944, he is eager, brave, and sometimes impetuous, earning the nickname "High School" from his peers. In the present day, he carries hidden emotional burdens from his wartime experiences while trying to impart the realities of combat to his enthusiastic great-grandson. He travels to the French village of Sainte-Régine to be honored for his service, fully aware that not everyone welcomes his return.

Trevor is a 12-year-old boy who idolizes his great-grandfather and is deeply fascinated by World War II. He heavily relies on video games to understand the conflict, leading him to view war as a glamorous adventure. He travels to France eager to see historical battlefields, though his perspective is challenged by the grim realities of history. Through his interactions with locals and his great-grandfather's sobering tales, he begins to see the human cost behind his favorite digital simulations.

Daniel is Trevor's father and a middle school history teacher. Divorced from Trevor's mother, he spends alternate weekends with his son. He strongly disapproves of the glorification of war and views his grandfather's stories with a critical, realistic lens, hoping the trip to France will teach Trevor the true cost of conflict. He acts as a stabilizing voice of reason, constantly reminding Trevor that real war breaks people and places.

Juliette is a 13-year-old French girl and a descendant of René Lafleur. She holds a deep-seated grievance against Jacob Firestone regarding events from the war. Along with her cousin, she actively follows the Firestones through France, struggling with the painful legacy of her family's past. She acts on the belief that American history books omit the true, devastating impact the war had on local French families.

Philippe is Juliette's hotheaded 17-year-old cousin. Deeply protective of his family's history and fiercely angry about the past, he uses his motorcycle to help track the Firestones across France. He is unwilling to easily let go of the long-standing resentments connected to his family's wartime suffering, preferring direct action over quiet acceptance.

René is a French farmer living on the outskirts of Sainte-Régine during World War II. As an active member of the French Resistance, he takes immense personal risks to shelter allied soldiers and fight against the Nazi occupation. He forms a vital alliance with American troops to liberate his village. Operating under constant threat of discovery, he utilizes his knowledge of the local terrain to coordinate strikes against German tanks.

Beau is a large, affable soldier from Texas who is part of Jacob's boot camp group. Initially assigned to a paratrooper unit, he is reassigned to the infantry and becomes a steadfast, loyal comrade in Bravo Company during their deployment to Europe. He relies on physical toughness and camaraderie to face the grueling daily reality of the frontline.

Freddie is a young army recruit who bonds with Jacob during their grueling time at Fort Benning. He ships out with Bravo Company to England and then to the beaches of Normandy, facing the immense pressures of the Allied invasion alongside his friends. He experiences the terrifying transition from training to active combat.

Leland is one of the original four young men who form a tight-knit group during basic training. He endures the physical miseries of camp, the transatlantic crossing, and the subsequent battles in France as part of Bravo Company. He operates alongside Jacob during dangerous bridge-clearing missions.

Julia is Trevor's mother and Daniel's ex-wife. She manages a busy household with Trevor and her two young twin daughters. She is initially reluctant to let Trevor miss three weeks of school for the trip but eventually agrees to the educational opportunity.

Kira and Kelsey are Trevor's six-year-old twin sisters. They look up to their older brother and often incorporate elements of his video game obsession into their own play, using their dolls to act out battles. They provide a lighter, innocent contrast to their brother's heavy focus on warfare.

Madame Lafleur is René's wife, a French civilian living on a farm near Sainte-Régine. She helps her husband harbor allied soldiers and manage their five children despite the constant threat of German patrols in the area. Her quiet bravery supports the entire local resistance effort.

Lieutenant McCoy is an American military officer overseeing Jacob's unit. He is a strict leader who heavily emphasizes the life-saving importance of digging proper foxholes to his reluctant young recruits. His unwavering demands prepare the soldiers for the harsh conditions of combat.