The lyrics of "whom the bell tolls" are based on the same-titled novel by Ernest Hemingway, published in 1940. In the Spanish Civil War, which was a preparation to World War II, an American is tasked with capturing a crossing controlled by the Fascism forces. After falling in love, he learned many unsettling facts about life and death.
This song serves as a criticism on how pointless war is. To indicate the direction, the song's final few lines deviate from the text.