Doyle, Sir Arthur Conan. "Danger! Being the Log of Captain John Sirius." Strand Magazine July 1914. Danger! and Other Stories. Project Gutenberg download.
Future-war work, of the very-close future variety, described by I. F. Clarke in Voices Prophesying War, ch. 3, as "Sir Arthur Conan Doyle's notorious short story of unrestricted submarine warfare, Danger, which won the interest of all Europe and the scorn of most naval experts" (p. 90). The story was written a year and a half before the outbreak of World War I. Clarke notes
Doyle was quite as deliberate as Wells had been [in War of the Worlds and elsewhere]. He wrote, he said, in order 'to direct public attention to the great danger which threatened this country'. He went to the nation with a story of the way in which the submarine fleet of one of the smallest powers in Europe defeated the entire might of the British Empire by sinking all vessels approaching UK ports.
Clarke quotes naval experts on the improbability of unlimited submarine warfare since civilized navies wouldn't have their boats torpedo and sink civilian merchants ships; and then, of course, they did, including the sinking of the Lusitania with the deaths of 1,198 passengers and crew. (Just how "civilian" the Lusitania was is still being argued, e.g., as we link here.)
See "Danger!" for a notable borderline case of very-near-future future-war SF combined with very much current propaganda.
RDE, finishing, 16Dec20