Pratchett Terry. Discworld 21. Jingo

Harper Voyager, 1998. ISBN-10: 0061050474.Ankh-Morpork has been at peace for a century, and so has Al-Khali. But now there are people on both sides who think it's time to give was a chance, and will happily help it on its way with a few murders.Modern war needs modern weapons. Unfortunately, Ankh-Morpork got rich making and selling them to Al-Khali. But it's just possible that salvation lies in the hands of the great inventive genius Leonard of Quirm, whose sketchbooks are filled with devices for killing people, flying through the air, and weighing cheese.