British air raid sirens sounded for the first time 22 minutes after Neville Chamberlain declared war on Germany. Although bombing attacks unexpectedly did not begin immediately during the Phoney War, civilians were aware of the deadly power of aerial attacks through newsreels of Barcelona, the Bombing of Guernica and the Bombing of Shanghai. Many popular works of fiction during the 1920s and 1930s portrayed aerial bombing, such as H. G. Wells' novel "The Shape of Things to Come" and its 1936 film adaptation, and others such as "The Air War of 1936" and "The Poison War". Harold Macmillan wrote in 1956 that he and others around him "thought of air warfare in 1938 rather as people think of nuclear war today".