Not martial arts -- it was a book on biological and chemical warfare in the ancient world. Things like poisoning arrows or wells, dumping burning crude oil on attackers during seiges, throwing scorpions at your enemies, Greek Fire... all sorts of dirty tricks people tend to overlook when they complain about how modern warfare isn't 'clean' and 'fair' the way things used to be. War has never been clean and fair.

Since my novel involves a multiple-front war, which is undeclared for most of the book, I thought it would be a good idea to know about underhanded tactics. Also, dirty tricks are often a cost-effective strategy when you don't have a lot of soldiers and are facing a more numerous enemy.