A Farewell to Arms follows Frederic Henry, an American serving as an ambulance driver with the Italian army during the First World War. While stationed in northern Italy, he begins a relationship with Catherine Barkley, a British nurse. After Frederic is wounded, Catherine helps care for him during his recovery in Milan, and their initially casual involvement develops into a serious attachment.

Frederic later returns to the front and witnesses the chaotic Italian retreat from Caporetto. Fearing execution by military police, he deserts and reunites with Catherine. The couple escape to neutral Switzerland, hoping to build a life away from the war. Their temporary peace ends when Catherine experiences a difficult childbirth. Their baby is stillborn, and Catherine dies from complications soon afterwards. Frederic leaves the hospital alone. The novel examines love, war, mortality and the attempt to find private meaning amid forces that individuals cannot control.