Just before the Second World War, the American naval historian (and science fiction author) Fletcher Pratt published a book on naval wargaming as could be done by civilians using ship models cut off at the waterline to be moved on the floors of basketball courts and similar locales. The scale he used was non-standard (reported as 1:666), and may have been influenced by toy ships then available, but as the hobby progressed, and other rule sets came into use, it was progressively supplemented by the series 1:600, 1:1200, and 1:2400. In Britain, 1:3000 became popular and these models also have come into use in the USA. These had the advantage of approximating the nautical mile as 120 inches, 60 inches, and 30 inches, respectively. As the knot is based on this mile and a 60-minute hour, this was quite handy.