When For Whom the Bell Tolls was published in 1940, it immediately became a resounding critical and popular success and helped cement Ernest Hemingway's reputation as one of America's foremost writers. Readers praised its realistic portrait of not only the political tensions in Europe that would soon erupt into World War II but also the complexities of the entire experience of war for the individual who found him or herself fighting for a cause. Hemingway had previously explored this theme, most notably in his short story collection, In Our Time (1924), and in his novels The Sun Also Rises (1926) and A Farewell to Arms (1929). Yet his attitude toward his subject in For Whom the Bell Tolls reveals a subtle shift. While his previous works focused more on the meaninglessness of war, this novel ends with a reaffirmation of community.

For Whom the Bell Tolls chronicles the experiences of American college professor Robert Jordan, who has volunteered to fight for the Loyalist cause in the Spanish Civil War. His initial idealism is quickly tempered by the realities of war. Yet his courage enables him to remain devoted to the cause, even as he faces death. Hemingway's compassionate and authentic portrait of his characters as they struggle to retain their idealistic beliefs has helped earn the novel its reputation as one of Hemingway's finest.