Early on in The Riddle of the Sands, Erskine Childers' 1903 novel about espionage and conflict between the Great Powers, there's a moment that's either wildly prescient or a statement of simple, brutal facts. Carruthers, a minor employee in the British Foreign Office, has sought to escape London's late summer doldrums by accepting an invitation to join Davies, an old friend from Oxford, on a sailing expedition around the Frisian Islands, where the coasts of Germany and Denmark meet. Used to wearing white flannel and blue blazers on luxurious pleasure yachts, Carruthers is shocked to discover that the Dulcibella, Davies'...