For Whom the Bell Tolls is a novel by Ernest Hemingway published in 1940. It tells the story of Robert Jordan, a young American volunteer attached to a Republican guerrilla unit during the Spanish Civil War. As a dynamiter, he is assigned to blow up a bridge during an attack on the city of Segovia. It was published just after the end of the Spanish Civil War (1936–1939), whose general lines were well known at the time. It assumes the reader knows that the war was between a democratically elected, pro-working class and anti-Catholic government, which many foreigners like Robert went to Spain to help, and a successful dictatorial, Catholic, pro-landowner revolt, supported by Nazi Germany and Fascist Italy. It was commonly viewed as the dress rehearsal for the Second World War, which in 1940 was just beginning. The novel is regarded as one of Hemingway's best works, along with The Sun Also Rises, A Farewell to Arms, and The Old Man and the Sea.

https://en.wikipedia.org/wiki/For_Whom_the_Bell_Tolls