The common point of the works mentioned in the passage is that ……..

Apart from the two world wars, the Spanish civil War was the bloodiest conflict in the first half of the 20th century. It lasted two years and 254 days. During that time about 1 million people perished. Of those million approximately 600,000 were battle-related deaths -more than in the American Civil War, which lasted longer. There were massive executions of the folk by the Nationalists. Vividly remembered even today is their bombing of Guernica on April 26, 1937, commemorated in a painting by Pablo Picasso. The war also became a subject of much literature. The most comprehensive one-volume history is The Spanish Civil War by Hugh Thomas. The most moving non-fiction work is George Orwell's Homage to Catalonia. The best-known novel is Ernest Hemingway's 'For Whom the Bell Tolls'.