Joey is a bright red bay horse with a black mane and tail, a white cross on his forehead, and four even white socks. Bought to work on a farm in Devon, England, he possesses a fighting spirit and deep loyalty to those who treat him with kindness. He learns to respond to a specific owl whistle, a sound that cements his deepest bonds. As the narrator, he observes the human and animal world with remarkable emotional intelligence.

Albert is a thirteen-year-old farm boy living in Devon. He possesses a gentle but determined nature, proving willing to be stern when necessary to train and protect his animals. He dreams of joining the cavalry to stay close to his beloved horse. He is fiercely loyal to those he loves and strongly disagrees with his father's drinking habits.

Topthorn is a tall, shining black stallion belonging to Captain Jamie Stewart. He holds his head with majestic dignity and possesses immense stamina. He serves as a brave and reliable partner during long marches and frightening artillery fire. He provides vital comfort and strength to the horses around him during highly stressful situations.

Father is an aging farmer in Devon who struggles with the heavy financial burden of his mortgage. He frequently turns to alcohol to cope with his stress, making him irritable and occasionally cruel to his family and animals. Despite his harsh exterior, he harbors genuine worry for his family's future and feels guilt over his desperate choices.

Captain Nicholls is a tall, elegant officer in the British cavalry who sketches in his spare time. He is a kind and gentle man who harbors deep anxieties about the incoming realities of modern warfare. He treats his mounts with respect and tenderness, recognizing the heavy burden placed upon them.

Trooper Warren is a young apprentice blacksmith drafted into the cavalry due to his father's obligations to a local squire. Though he lacks finesse in the saddle and rides poorly, he is incredibly gentle with his horse on the ground. He frequently talks about his family and his life back home to maintain his spirits.

Friedrich is an older German soldier whom others call "Crazy Old Friedrich" because he frequently talks and laughs to himself. He is a kind, gentle man whose entire nature rejects the violence of the war. He only remains in the army to avoid bringing shame to his family back home.

Emilie is a thirteen-year-old French girl living on a farm requisitioned by the German army. She is a tiny, frail creature who nonetheless leads the massive war horses around with complete confidence. She treats the horses as her closest friends and dreams of keeping them forever.

Grandfather is an elderly French farmer caring for his granddaughter on their requisitioned property. He is a sensitive, hardworking man who has endured significant loss during the conflict. He acts as a fierce protector of his family and deeply values the comfort the horses bring to his home.

Mother is a hardworking farm wife in Devon who frequently acts as a mediator in her household. She understands the intense financial pressures driving her husband's destructive behavior and pleads with her son to see the good in him.

Captain Jamie Stewart is a British cavalry officer who rides a magnificent black stallion. He is realistic about the severe conditions of the war and deeply values the strength and stamina of his mount during terrifying battles.

Corporal Samuel Perkins is an ex-jockey who trains horses for the British military. He is universally feared by troopers and horses alike for his harsh methods and strict adherence to discipline.

Zoey is a kind, older farm mare living in Devon. She works reliably in the fields and serves as a comforting, steady presence for the younger animals on the property.

David is a soldier in the British Veterinary Corps who used to run a fruit cart in London. He takes his duty to care for the army's animals seriously and frequently offers practical support to his friends in the camp.

Major Martin is an officer and veterinarian in the British army. He balances a realistic view of medical odds with a genuine dedication to treating injured animals whenever possible.

Sergeant Thunder is a commanding but supportive non-commissioned officer in the British Veterinary Corps. He strictly maintains military discipline while actively looking out for the welfare of the men and horses under his command.

Herr Hauptmann is a tall German officer who holds deep respect for bravery on the battlefield. He ensures that animals who perform heroically receive immediate food, water, and shelter rather than being treated purely as equipment.

Maisie Brown is a young woman from Albert's village in Devon who works as a baker. She has beautiful blue eyes and golden hair, and she occupies much of Albert's thoughts while he is away at war.

Rudi is a young German soldier who worked as a farmer before joining the conflict. He appears no older than a child in a uniform and holds a deep appreciation for fine horses.

Heinie is a strong, tall horse assigned to pull heavy artillery for the German army. He possesses the necessary size and strength to act as a lead gun horse alongside the other large animals.