In July 1914, a famous British novelist published a short story in The Strand Magazine imagining how a small European country could starve Britain into surrender using submarines against merchant shipping. Twelve naval experts mocked the idea in the same issue. War broke out a month later. Eight months after that, German U-boats began doing exactly what he had described.

His name was Arthur Conan Doyle. By 1914 he had killed Sherlock Holmes, brought him back, fought as a volunteer surgeon in the Boer War, and become the most-read living novelist in the English-speaking world. He had also written letters to The Times for a decade warning that submarines would change the next war. The Admiralty treated this as fantasy. In the spring of 1914, Doyle decided to make the case concretely. He sat down and wrote a short story.

Danger! Being the Log of Captain John Sirius was published in The Strand in July 1914, six weeks before the assassination at Sarajevo. The story is told from a submarine commander's point of view. He commands eight submarines of a fictional small country called Norland. Over the course of the story he sinks British merchant shipping faster than the Royal Navy can replace it. He torpedoes a famous British ocean liner off Liverpool. The British government surrenders to avoid starvation. The same issue of The Strand carried an article called What Naval Experts Think, in which twelve British naval officers explained why no civilised nation would ever sink unarmed merchant ships, and why submarines would in any case be irrelevant.

War broke out on the fourth of August, 1914. In February 1915, Germany declared the waters around the British Isles a war zone. German U-boats began sinking merchant ships without warning. On the seventh of May 1915, U-20 torpedoed the Lusitania off the coast of Ireland. Eleven hundred and ninety-seven passengers and crew died. By April 1917 the Admiralty had calculated that Britain had six weeks of food left. The convoy system was adopted on the twenty-fourth of May. It saved the country at the last possible moment. Doyle later described his own story as singularly prophetic.

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