History books are written by historians, and military history books are written by military historians. Rather naturally these people are focalized on their object of study, which most often is a single subject. The kind of book you ask about could probably be written only by wargamers.
you can’t divorce military history from history.
Of course. And it’s not only about causes. Changes in battle tactics, etc, don’t happen on their own they depend on geography, technology, economy, politics, etc. So if you want a larger picture, be prepared to have a look at all these.
Two quick examples I have found interesting:
– A discussion (in a forum that I don’t visit any more) where someone asked a question about 11th century Norman and Breton light cavalry. I tried to help. You must think about all elements to suggest an answer (and even then I know it’s only a guess). http://theminiaturespage.com/boards/msg.mv?id=239426
– France invaded Algeria in 1830. It had awful consequences for 132 years, but that’s another matter; as wargamers we can see other sequels: the French army had to adapt to skirmish fighting in a wild climate (long before the big colonial era of the late 19th C.) and had to experiment new tactics for light infantry. And: (1) I’ve read in English history books that the British army arriving in Crimea in 1854 suffered from lack of tents etc whereas the French army was well equipped. I don’t think any of the HQ involved was better than the other, but the French had new designs of tents because of what they had just learnt in Algeria; (2) “Hardee’s Rifle and Light Infantry Tactics” manual, widely used by both sides in the ACW, was copied on a French Light Infantry manual — directly inspired by the French experience in Algeria.
Ahem. Perhaps wargamers should write military history books?