Tiberius said:Hence helots.
Yeah, well, the OP spoke of "every able-bodied citizen". Sure, you can say that helots are not fully citizens, but there are two upshots of this:
1)The size of the resulting army is probably much smaller that some might be imagining, as a large portion of the population isn't elegible.
2)The empowered ruling class of citizens is constantly losing people in wars, while the helots are not.
Somehow, I figure (2) is not what you'd call a politically stable upshot, especially in a world when some of those helots will probably turn out to be sorcerers and clerics...