For any Freeper's interested, there was a quite prescient volume written on this subject qquite some time ago: "A History of Warfare", By John Keegan.
I heartily recommend it to anyone interested in the methods and motivations of ancient warfare. Without the political correctness.
It has the added bonus of turning Clauswitz on his head.
Just a suggesstion.
I would also suggest "War" by Gwynne Dyer. Dyer is a bit of a lib, but his approach to the subject -- especially ancient warfare -- is pretty enlightening.