What was the first ever book written on a war that was turned into a movie?

I have to write a research paper comparing the book The Short-Timers and the movie which it was turned into, Full Metal Jacket. So, to start the thesis, I want to talk about the first war movie ever and the first war book. Then, the first book on war that was turned into a movie and all that. I can't find this information anywhere; can anyone help? :] thanks.|||The first book about a war that was eventually turned into a movie (several of them, in fact) was probably something like Homer's "The Iliad." That might have even been the first war book, at least in Europe - though it's impossible to say that with any certainty. (There were books about wars in China that are centuries older than that.)|||Well, the earliest war movie I can think of is "Birth of a Nation," a 3 hour silent film from 1915 about the Civil War.