For Whom the Bell Tolls was inspired by Hemingway's experiences as a foreign correspondent, first in Paris and then in Spain itself, during the Spanish Civil War. Hemingway visited Spain in 1931, just after the monarchy of Alfonso XIII had been overthrown. After several years of political conflict and civil unrest, elections were held in Spain. The resulting parliament was evenly divided between leftists and rightists, creating a very volatile political situation. It was then that Alfonso XIII voluntarily exiled himself and on April 13, 1931, the Republic was proclaimed. .
Hemingway, observing these events, predicted that a civil war would erupt between the leftist and rightist political factions. He was correct, and when the Spanish Civil War began in 1936, Hemingway wrote articles and delivered speeches to raise money for the leftist, now called the Loyalist, cause. In 1937, Hemingway traveled to Spain to cover the war for the North American Newspaper Alliance. Only a few months after his arrival, Hemingway announced to the literary world that he was working on a new novel- its subject was the Spanish Civil War. .
An American named Robert Jordan, fighting on the side of the Loyalists during the Spanish Civil War, is sent behind fascist enemy lines to blow up a bridge in coordination with a larger offensive being mounted by the republicans. Jordan meets up with a group of guerillas led by Pablo, a man sliding into drunkenness and decline, and his partner, Pilar, a strong-willed woman who holds the band together. He meets Maria, a 19-year-old girl living under Pilar's care after having been rescued from a prison train by the guerilla band. Jordan and Maria immediately fall in love. .
Jordan spends three days coordinating the operation and trying to hold the band of guerillas together in spite of Pablo's weaknesses. Despite the fact that it is May, a heavy snow falls in the mountains, and the band must face the threat of possible discovery, since the fascist cavalry patrolling the mountains can use the snow to follow their tracks.