Isegoria has a series of posts that covers the topic in a way that I've never seen before. If you are a military history enthusiast, then you should take a look.
The Macedonian Army
A Semi-Barbarian Upstart
Diplomacy and Logistics
That last one is particularly interesting - the old saw goes that when conflict looms amateurs talk strategy while professionals talk logistics. It also casts some light on the gap in time between Alexander's first two big battles with the Persians, and the final one.
I'd like to see a post about the dynamics of the Persian Empire itself. It expanded rapidly and collapsed quickly.