The novel opens behind the German lines of the Western Front in World War I during the summer of 1916. Paul, Tjaden, Müller, Albert and a few others are eating. They all volunteered to be soldiers for this war and are just beginning to question the wisdom of the schoolteachers who encouraged them to enlist. Today, their food supplies are bountiful because the cook prepared food for 150 men, but only 80 have returned from battle. Paul and his buddies visit the hospital to see a stricken friend – the hospital exudes a vibe of incompetence and little compassion for the wounded.
The narrator gives us some background and highlights characters. Kat, 40, is the respected leader of the group and is admired by Paul for his practical skills and gut instincts. He is contrasted with Himmelstoss (a former postman), who is largely incompetent, but has embraced every ounce of power his military rank has given him.
Paul revisits his friend Kemmerich in the hospital and watches him die. Hospital orderlies quickly remove his body so another can take the bed, and Kemmerich's coveted boots become property of Paul's friend Müller.
Relatively young reinforcements arrive for an operation to put up protective fence wire against the advancing enemy, British and American troops. The men eat well before the mission and discuss the irony of their situation – those in power are idiots, teachers are untrustworthy, the discipline around camp is meaningless. Himmelstoss accosts the group with orders. They wait to get back at him until one night, when he's leaving a pub drunk. They turn on him, mug him, hold him down, and literally whip his butt with a switch. They feel like 'young heroes.' And the stripes that now decorate Himmelstoss's bare bottom mirror the multiple stripes on a military outfit, which are supposed to conveying rank and respect.
The troops launch into their assigned barbed wire fencing mission at the Front. Noisy jeeps, loud guns, smoke, bomb craters, and nerve gas are all seemingly inches away. They are bombarded at night by shells as they race to roll out the protection wire – it is clear that they are in defense mode, just hoping to slow the speed of victory by the Alliance (the British, French, Russians, and Americans).
Troop 9 finishes their wiring and are bombed heavily on the way back. Fire, gas, and darkness accost the retreaters. Ironically, they take shelter in a graveyard, where they toss corpses out of coffins to hide in them.
Back at base camp, Paul and his friends eat, smoke, and fantasize about all that they are missing. Himmelstoss returns to try and order the men around – the recent battle was his first experience on the Front, and it has made him less reliant on the power of stripes on his uniform. But he still presses, is disrespected, and storms off. The men review their dead and condemn the rules of military hierarchy as they apply to the Front, where rules are simply different. The men are brought to a field judge who notes Himmelstoss's petty cruelties and lets them off easy for disrespecting him. To celebrate, they catch and cook a wild goose.
As they prepare for an offensive onslaught by the enemy, they are accosted by rats, which they kill in creative ways. Then they are bombarded at night, which drives the youngest recruits to insane and suicidal acts. Next comes hand-to-hand combat. In the terror and violence, Paul realizes that he and his fellow soldiers are becoming wild beasts. They listen at night during the quiet to the sounds of dozens of men dying in the brush, unable to be rescued by anyone.
The men recuperate farther back behind the Front, and recount the dead and the terror of battle. While the men are resting up, they meet a few French women who covet the bread and sausages they offer. Paul and his friends swim naked across the river to meet up with the ladies, exchanging food for the women's company.
Paul is given two weeks' leave and returns home to his mother, who is sick with cancer, and his father, who is insensitive and eager for stories of battle. Paul feels alienated, realizing that anyone who hasn't been on the Front can't understand what he has undergone. He retreats further into himself during his stay at home. On duty, he visits the dead Kemmerich's mother and lies to convince her that her long-suffering son died instantly. Paul also visits his schoolteacher, Kantorek, the one who convinced him and his friends to enlist. He chides his former teacher for painting a false picture of the war as an honorable way of defending the fatherland. Returning to the Front, Paul regrets ever having gone home.
Paul is sent to a special training camp next to a war prisoner compound. As lacking as he has felt in resources, he feels wealthy compared to the mostly Russian prisoners who beg for his garbage. He gives them some of the cakes that his mother baked for him.
Paul is back on the Front, guarding a bombed schoolhouse, preparing to enter Russia. Violent images accost him on the journey – naked bodies of soldiers whose clothes were literally blown off them, headless corpses, severed body parts… Paul and the other soldiers are shelled along the way and hide in previous shell holes for protection. The Front has shifted – it shifts right over Paul as enemy soldiers literally run over him. When surprised by one, he instinctively kills him – a French soldier – and waits with him, almost apologetically, as the man dies slowly. Rifling through the man's wallet and seeing his family pictures, Paul promises to write to them.
The group is given a job guarding an abandoned village. They expect boredom. They discover some baby pigs, which they kill and eat – and then get diarrhea. They are sent to evacuate a village, and fleeing Russian families silently pass by them, heads down. On the way, Paul and the other soldiers are bombed, and many are injured.
At a Catholic hospital, they fear the surgeons who treat them like science experiments. Most of the nurses/nuns are robots; one is kind. Paul has a plaster cast on his leg and fights for the right to urinate privately. The men are awakened by the din of prayers, and throw a bottle to make the nuns to shut the door and let them sleep. Paul's friend Albert is sent to The Dying Room from which nobody returns. Paul slowly recovers and can walk – and is sent back to the Front.
With resources scarcer than ever, men tired, and morale ebbing lower, Paul grows ever more philosophical about their demise on many levels: he ponders Youth, Hope, Order, Spirit, and Trust. A soldier named Detering deserts but is captured. Berger tries to euthanize a dog and is shot in the process – as is the orderly who tries to rescue Berger. Müller is shot point blank. The remaining men are starving. When Kat is shot in the leg, Paul carries him for miles, only to discover that Kat was shot in the head and died while Paul was hauling him. Among his group of friends, Paul is the only survivor.
Then, on a reportedly quiet day in October 1918, Paul dies. "His face has an expression of calm, as though almost glad the end had come" (12.12).