The Riddle of the Sands by Erskine Childers is a novel published in 1903 that belongs to military fiction or "invasion novels." It predicts pre-First-World-War threats of German invasion of the British Isles. The pertinence of Childers's ideas and details, which have been based on his own sailing experience, has made the historical British Prime Minister Winston Churchill summon him up at the outbreak of the war for advice. The fiction tells about two friends named Carruthers and Davies who go on a sailing trip onboard of their small yacht named Dulcibella to explore the area of the Frisian Islands after suspecting the German army of having some wicked enterprise in the area. Their doubts are eventually confirmed when they discover a German military base getting ready to invade Britain. After some misadventures in the site, the couple manage to flee back to their country to inform the British authorities and help them ward off the German conspiracy. Though fictional, Childers's book has a great influence on the British public opinion as well as on decision-makers. With other publications by the same author and by other authors influenced by him, the novel raised awareness of the German threat during the period preceding the First World War and of the unpreparedness of the British forces.