Being the Log of Captain John Sirius", was (the preface notes) written 18 months before the outbreak of World War I, and first published in the Strand Magazine in July 1914.

It depicts a hypothetical scenario in which a small, fictional European country manages to defeat the United Kingdom by innovative naval strategy using a new technology, the practical combat submarine.

It is also a monarchy, whose monarch seems to retain actual executive power; the crucial policy meeting in which it is resolved to defy a British ultimatum and embark on submarine warfare is attended by the king, the foreign secretary, an admiral, and Captain Sirius; a prime minister is conspicuously absent.

Unusually in the invasion literature genre, the story is narrated in first person by Captain Sirius, the victorious enemy commander; while he is portrayed as a professional soldier who does not delight in killing, his chauvinism and veiled contempt for the UK were clearly intended to evoke a patriotic reaction from British readers.

[2] Admiral Eduard von Capelle testified before the Reichstag that Gentlemen, it is well known that there was published in England before the war a pamphlet which described U-boat warfare in an absolutely masterly manner and which attracted a great deal of attention.