Lieutenant Frederic Henry is an American volunteer ambulance driver for the Italian army during World War I. Not much is known about Henry's life before the war, his motivation for joining the Italian army, or the family he left behind. He embodies many of Hemingway's ideal masculine qualities: he is brave, sexual, and stoic. He loves women and alcohol, using both to escape reality during the war. When he first meets Catherine Barkley, he is only interested in bedding her, but during his hospital recovery, he truly falls in love with her. Throughout the novel Henry struggles with his spirituality. He wants to believe in something to give his life greater meaning, but he can't comprehend a God that would allow the mindless suffering and loss Henry has seen in the war. His love for Catherine becomes his religion, giving him something to sacrifice for. In the end he learns that life is meaningless and death indiscriminate.
Catherine is a British nurse's aid sent to the front during World War I. When she meets Henry, she is grieving the loss of her fiancé, who died in battle in France. Heartbroken, Catherine engages in a complicated game of seduction with Henry because she would rather have an illusion of love, however false, than nothing at all. As the novel progresses, the lines between fantasy and reality blur, and the reader is left questioning whether she loved Henry at all or if the entire romance was a game. Despite Catherine's complicated emotional state, it is clear that she is brave, dedicated, and faithful. In her pursuit of creating the idealized romance, she would say or do anything to become Henry's perfect woman. She is obsessed with appearances and "being good." When she becomes pregnant, she worries that this will complicate her fantasized romance. Before she has to face reality in the idealized life she has constructed, she dies.
When talented Italian army surgeon Rinaldi is introduced to the reader, he is an effervescent man whose love of alcohol, women, and debauchery breathes passionate excitement into the depressing battlefield setting. When Henry returns to the front after his injury, Rinaldi has become dark and embittered. He drinks excessively now, but it makes him angry rather than charming, and he has contracted syphilis. Rinaldi is a prime example of wartime disillusionment and the dark effects battle has on a soldier's soul.