The novel is presented in five books. Unless otherwise stated, it is assumed that the narrator is speaking in Italian when conversing with Italians and in English when conversing with British or American characters.
The novel begins on the Italian-Austrian border during the First World War. The story is told in the first person. The narrator opens the story with a description of late summer in a small village near the mountains. There is a river and a plain beneath the mountains where the armies are fighting and at night the flashes from the artillery are visible in the village. The weather is pleasant and gradually changes from summer to autumn. Many troops and military vehicles pass through the village on their way to the front. Occasionally the Italian King passes through the village in his motorcar on the way to inspect his troops. The war goes badly for the Italians and then the winter rain brings a cholera epidemic. The narrator notes that "in the end only seven thousand died of it in the army."
The following year the war goes better for the Italians and the narrator describes the fine house and the town of Gorzia where he resides during this period. Although only less than a mile from the fighting in the mountains, Gorzia has mostly been spared from destruction and swells with the increased wartime activity. It has cafes, hospitals and bordellos, one for enlisted and one for officers. Outside the town, however, there is much damage from battles. On the day of the first snowfall, which marks the end of the season for fighting, the narrator is walking in the remains of the forest. Later, he sits in the bordello for officers, drinking asti with a friend who, upon seeing the priest from their mess, jokingly indicates that the priest should join them. That evening, after the mess of spaghetti and red wine, the captain begins his regular harassment, or "priest-baiting", of the priest. He accuses the priest of having been with girls and the priest, embarrassed, shakes his head. The captain makes a rude joke and comments that the Pope wants the Austrians to win the war. He declares himself to be an atheist and recommends an anti-Catholic book to the narrator. The narrator changes the subject and suggests that with the coming of the snow the fighting will cease for awhile. The major enthusiastically suggests that the narrator should go on leave and see some of the country. A lively discussion develops as to where the narrator should take his leave and the priest describes the simple pleasures to be found hunting in his native mountain village of Abruzzi. The captain begins a lewd finger-shadow game to illustrate the girls of Naples and the group elects to go the bordello. The narrator says goodnight to the priest before he leaves to join the others.
The winter has passed when the narrator returns from his leave to find that his unit is still living in the same town. It is spring and the countryside is full of new life. The narrator notices that there are more artillery pieces placed around the town and that more of the buildings have been damaged by shellfire. The house he occupied the previous fall is the same as when he left and he goes to the upstairs room he shares with lieutenant Rinaldi, a likable and exuberant surgeon with whom he has become friends. Upon entering the room, he sees that his things are where he left them. Rinaldi, who is lying on the other bed, wakes up when he hears his friend enter the room. The narrator tells Rinaldi that he had a "magnificent" time on leave and Rinaldi, overjoyed at his return, greets his friend with a kiss. The narrator says that he went "everywhere" but admits that Milan was the best. Rinaldi immediately grasps the truth of the situation and asks about the woman he met in Milan with questions such as "where did you meet her" and "did you stay all night" to which the narrator responds that he in fact did "stay all night."
Rinaldi explains that they now have many new beautiful girls in the village bordello, new to the front, as well as several pretty English nurses. He cavalierly confesses that he has fallen in love with one of them, Miss Barkley, and insists that the narrator accompany him on his next visit to her. The narrator describes Rinaldi as "good-looking, was my age, and he came from Amalfi. He loved being a surgeon and we were great friends." Rinaldi borrows fifty lire from the narrator before going back to bed.
At that evening's mess, the narrator discovers that the priest is somewhat hurt that he did not go to visit the priest's family in Abruzzi during his leave. After some explanation and a great deal of drinking, the priest understands that the narrator would have liked to have gone but people very rarely get to do what they want. The narrator admits to himself that he did not go to any simple and pure mountain villages like Abruzzi, but spent his furlough in smoky cafes drinking to excess and sleeping with strange women; activities followed by mixed feelings of pleasure and repulsion for the excesses. The narrator tries to explain all this to the priest and the priest understands his friend's weaknesses and they are still friends. The priest-baiting captain interrupts their conversation by declaring that the priest is not happy without girls, wants the Austrians to win the war and never wants the Italian army to attack. The priest denies all the accusations and the major asks that the priest be left alone. The mess adjourns.
The narrator is awakened in the morning by the sound of an artillery battery in the next garden firing shells over the house toward the enemy. He admits that it is a nuisance, but is glad that the gun is not any bigger. After coffee in the kitchen he visits the garage to inspect the ambulances. He finds ten blunt-nosed ambulances being tended to by mechanics. He asks one of the mechanics if the battery in the next garden is ever shelled by return fire and is satisfied to learn that it is not. The Italian enlisted men refer to him as "Signor Tenente" which reveals his rank in the Italian army to be that of Lieutenant. The mechanic explains that one of the cars is broken but the others work fine. When the same mechanic asks him if he had a good time on leave, all the other mechanics grin knowingly. After inspecting the other cars, the narrator comes to the realization that it did not matter whether he was personally there or not and the task of retrieving the wounded and maintaining the cars had continued successfully without him. He returns to the kitchen for more coffee before visiting the posts in the mountains. He returns to the village in the late afternoon.
The narrator explains that during the offensive that was to begin soon, the troops would cross the river above a narrow gorge and attack up a hillside. The ambulances would have to be stationed very near the river to pick up the wounded and transport them back to the hospital.
The narrator returns to the room and finds Rinaldi dressed cleanly and reading a copy of Hugo's English Grammar. Rinaldi insists that he accompany him to visit Miss Barkley and after initially refusing, the narrator eventually agrees. The narrator cleans himself in the basin and before they leave, they each have two glasses of grappa. The British hospital is in a big villa and there they find Miss Barkley and another nurse sitting in the garden. Miss Barkley engages the narrator in conversation and remarks that it is odd for him, an American, to be serving in the Italian army. The narrator points out that it is only the ambulance corps but Miss Barkley persists in her assertion that it is odd. The narrator remarks that "there isn't always an explanation for everything" and Miss Barkley counters that she was raised to believe that everything has a reason. Miss Barkley asks if they have to continue talking "this way" (meaning formally and without touching upon personal subjects) and the narrator admits that they do not.
The narrator describes Miss Barkley as tall; wearing a white nurse's uniform with long blonde hair, tawny skin and gray eyes, and very beautiful. She carries a thin rattan stick that upon questioning she explains belonged to a boy who was killed in the Battle of the Somme. They had been engaged for eight years and had known each other all their lives. She explains that she was pledged to marry him but had postponed the date because she thought it would be bad for him to go to war with a wife at home. Miss Barkley asks the narrator if he has ever loved anyone and he answers that he has not.
The narrator compliments Miss Barkley's hair and she explains that she wanted to cut it off after her fianc� died. She wishes she had given him something because she didn't care about "the other thing and he could have had it all." She admits that she knows "all about it now. But then he wanted to go to war and I didn't know." The narrator asks the other nurse's name and Miss Barkley says that her name is Helen Ferguson. She asks if his Italian friend is a surgeon and the narrator explains that he is a very good surgeon. Miss Barkley is relieved to find a good surgeon so close to the front. She calls it a "silly front" but observes that it is very beautiful. She explains that she got into nursing when her fianc� entered the war. She admits that she had the "silly notion" that her fianc� would show up in her hospital with a picturesque wound like a saber cut that she could heal. She goes on to remark that if anyone ever saw the horror of the front in France, the war couldn't possibly go on. Her fianc�, she explains, was blown to bits by artillery. She asks if the war will ever end and the narrator says that it will crack somewhere. Miss Barkley is of the opinion that the French and British will crack in France because battles like the Somme can't continue to happen. She does not think the Germans will crack.
Miss Ferguson and Rinaldi are drawn into the conversation and Rinaldi is confused to find out that Miss Ferguson is from Scotland, which is not part of England. Walking home, Rinaldi observes that Miss Barkley prefers the narrator but that the Scotch nurse is nice. When the narrator asks if Rinaldi likes the Scotch nurse, Rinaldi says that he does not.
The following afternoon the narrator returns to the British hospital to visit Miss Barkley. The head nurse asks why he is in the Italian army and the narrator responds that he happened to be in Italy and spoke the language. He asks if it is too late to join the British army and she says that it is. The head nurse tells him that Miss Barkley is on duty but he can return at 7:00 PM to see her.
The narrator describes his activities of the morning, which had included going up the river to the spot where the next offensive would occur. The Italians had held a bridgehead across the river only a few yards from the Austrian lines. The small town that had formerly occupied the spot had been reduced to rubble. While walking among these ruins, now full of artillery emplacements, dugouts and signal rockets, the narrator encounters a captain that he knows and they share a drink. The narrator returns to the Italian side of the river to survey the new road being built to transport men and materiel to the launching point. He notes that the ambulances will go down the new road and wait in a sheltered spot for the wounded to be brought across the pontoon bridge from the dressing station and there to the hospital via the old, narrow road. On the way back to Gorizia, the narrator encounters a spot where several large shells have just landed and two Italian sentries hold him up before he can proceed.
After dinner, he returns to the British hospital and finds Miss Barkley with Miss Ferguson. After much excuse making, Miss Ferguson leaves them. Miss Barkley, whose first name is Catherine, briefly discusses her role as a V.A.D., a sort of nurses' assistant and then, at the narrator's request, they try to talk about something other than the war. He holds her hand and she does not resist until he tries to put his arm around her. He attempts to kiss her and she slaps him. She immediately apologizes by saying that she "just couldn't stand the nurse's-evening-off aspect of it" and he reassures her that she did right to strike him. The narrator comments that he was "angry and yet certain, seeing it all ahead like the moves in a chess game." She gives him permission to kiss her again and he does so forcibly until she shivers in his embrace and begins to cry on his shoulder. She asks him to be good to her because they will have a "strange life together." The narrator thinks she is a little crazy but humors her in her emotional state. He walks her to her villa and then returns to his room where Rinaldi accuses him of having "that pleasant air of a dog in heat."
After two days at the posts, the narrator returns to the village but he is too late to see Miss Barkley until the following evening. While he waits for her in the hospital's office, he notes the great quantity of marble busts in the corridor. He thinks about the steel helmet he wears at the front and the English gas mask he has just received. He can feel the weight and bulk of the Austria 7.65 caliber pistol he is required to wear pressing into his back. He feels ridiculous carrying a pistol, especially one with such a barrel so short that he can't hit anything, but is able to forget about it except as a "vague sort of shame" when in the presence of English-speaking people.
Miss Barkley appears and greets the narrator formally by calling him Mr. Henry [the first time in the book that the narrator's name is used]. They go to the garden to get away from the eavesdropping orderly in the office. In the garden she refers to him as "darling" and wants to know where he's been and why he could not send a note. She insists that he call her by her first name and asks if he loves her. He lies and tells her that he does. She asks him to say "I've come back to Catherine in the night" and he does. She confesses that she loves him. He kisses her and seeing that her eyes are shut he kisses them as well.
He notes to the reader that he did not care what he was getting into, only that it was better than going to the officer's bordello. He considers the courting to be a sort of game like bridge with stakes. After kissing her for awhile standing, up he remarks to the reader that he was "experiencing the masculine difficulty of making love very long standing up."
They sit on a bench, but she will not allow him to put his arm around her. Her mood suddenly shifts and she admits that they are playing a "rotten game." She says that he is a nice boy and does not have to love her. He lies that he does and she tells him not to lie, and though she had a "very fine little show" she's well again. She insists that she is not crazy, only a little off sometimes. He promises to come and see her again and obtains one more kiss, which she breaks off prematurely and leaves.
He confesses to the reader that he liked to watch her move. He passes by the Villa Rosa (the bordello) but proceeds home. Rinaldi returns drunk from the Villa Rosa soon thereafter and declares that he is glad he did not become "involved with the British."
In this first section of chapters, Hemingway's use of first person narration and typically lean writing style means that the reader is introduced to the world of the story suddenly and is left to discover the circumstances from the narration. Over the course of these chapters, for instance, we learn without being explicitly told, that the narrator's name is Frederic Henry and that he is an American serving as a lieutenant ambulance driver in the Italian army. Although he takes his responsibilities seriously, evidenced by his attention to detail, he feels no great loyalty to the Italian cause. For him, the war is not a question of patriotism but of time and place. As he admits to Catherine Barkley on their first meeting, he doesn't know why he joined the Italian army only that he happened to be in Italy at the time. He is outgoing and thoughtful but unwilling to emotionally commit to any one person or ideology. Rinaldi is his partner in this outlook, but Frederic's obvious sympathy for the priest belies a deeper inner life. Nevertheless, his perception of his burgeoning relationship with Catherine as being nothing more than a game with carnal satisfaction, as the implicit object reveals him to be at this point in the story, is somewhat shallow. Catherine, on the other hand, has been deeply affected by the loss of her fiance on the western front. She is emotionally vulnerable but possesses a keen intellect and a willingness and ability to detach herself from the course of ordinary life. Their attraction is almost immediate.