World War I began in 1914 and ended on Nov. 11, 1918. Fought primarily between the Triple Alliance powers of Germany and the Austro-Hungarian Empire and the Triple Entente countries of England, France, Russia, Italy, and the U.S. (Italy defected from the Triple Alliance in 1915; the U.S. joined the war in 1917), the Great War, as it was called, with its vast scope, modernized weaponry, and vague political struggle over land, laid waste to Europe's landscape and population. Roughly half of the 70 million men and women serving in the war were killed, injured, or taken prisoner.
A Farewell to Arms is greatly informed by Hemingway's own wartime experience. Rejected from the U.S. army for his poor eyesight (which he later falsely claimed was due to boxing), Hemingway's determination to join the war effort landed him a post with the Red Cross as an ambulance driver on the Italian front. He jumped at the chance to be a canteen-provider on the front lines, handing out chocolate and cigarettes to the troops during battle, and on July 8, 1918 he was hit in the leg by an Austrian mortar shell. Despite the wound, he managed to carry an Italian soldier to the nearby command post. However, machine-gun fire struck him in the knee and foot, and he was eventually sent to a hospital in Milan, Italy. A similar injury befalls Henry in the novel.
During his convalescence, the 19-year-old Hemingway had an affair with an American Red Cross nurse seven years his senior, Agnes von Kurowsky. This experience inspired Henry's romance with Catherine in the novel, though Hemingway most likely embellished it; most scholars believe Agnes, a committed nurse, never let him move beyond kissing and did not reciprocate his intense feelings. Though she did not die during the war, as Catherine does, Agnes eventually rejected Hemingway via a letter.
The painful emotions of a broken body and heart no doubt embittered Hemingway. A Farewell to Arms (1929), which some critics consider the finest novel to come out of the war and Hemingway's personal best, reflected the widespread disillusionment with war - and with a world that allows such barbarity - of Hemingway's young but weary post-WWI "Lost Generation."