I wasn't sure where to take this question so figured I'd just ask a historian. I'm writing a war film and need as much info on how war is conducted as possible.
Which cultures are you interested in?
Arab Bedouin raiding as a form of war strategy is going to be very different from Japanese Bushido.
If you have access to a library (probably a university library), Fagan and Trundle (2010) put out an edited volume called *New Perspectives on Ancient Warfare." It's got articles about all sorts of ancient topics, such as chariot and cavalry in the early first millennium, Assyrian tactical systems, Achaemenid cavalry, Naval warfare and finance in archaic Eretria (Greek), Carthaginian naval questions, and Caesar vs the Helvetians.
The Skulking Way of War by Patrick Malone is an interesting read on how Native Americans and Colonists fought during King Philip's War.
Totally agree with the earlier comment - depends on which cultures you are interested in and also from what time? as things change a lot.
However, what maybe useful are the following books, although they are focused on near-east, middle-east and european theaters of war only and not other regions of the world:
Battles of the Ancient World (Kelly Davries, Martin Dougherty, Iain Dickie, Phyllis Jestice and Rob Rice) Amber Books, London, 2007
Battles of the Crusades (Kelly Davries, Martin Dougherty, Phyllis Jestice, Christer Jorgensen and Michael Pavkovic) Amber Books, London, 2007
Battles of the Medieval World (Kelly Davries, Martin Dougherty, Iain Dickie, Phyllis Jestice and Christer Jorgensen) Amber Books, London, 2007