I've read the FRCS, The Unapproachable East, and the Spellbound boxed set cover to cover on Rashemen and Thay, more times than I care to acknowledge (since I've been running a campaign in the region). I can't believe I overlooked that statement! That's an extremely poignant insight. If the "standing army" in Mulsantir is 500 of 4848, then it could be reasonsed that the "standing army" would be roughly comparable for the rural areas surrounding the city, and throughout Rashemen. This is 10.31%. To extrapolate this theory, using my numbers above, the area of Mulsantir, and surrounding rural settlements (combined population of 44,068 * 10.31% = 4,543). In theory, the standing army capable of rising to the defense of Rashemen in and around Mulsantir would be a force of approximately 4,543. These armies would be largely made up of Warriors and Barbarians, in light and medium armor, with little to no cavalry. Certainly a higher "percentage" of the population in a warlike position than most medieval fantasy settings would share.
The big remaining question would be how do you extrapolate a "militia" component, as a reserve to the armies? How much bigger can this army get? Twice it's size? Four times?
Silveras, as a quick note. I absolutely LOVE your thread about the different supplements available to support this type of thing. It is in part responsible for my contemplating such an endeavor. In light of some of the things I'm trying to accomplish, what product might you recommend to facilitate such a battle? Fields of Blood? (It seems to have gotten your best review thus far.)