It is proven that you can have an army that is larger than your total population. When you send people to training for your army, they are removed from your Idle Population pool, and the population will slowly grow over time to replace those people.
Armies do no desert because of low population, because they are not members of your population anymore. Armies desert when they run out of food to pay for their upkeep. When I tried this, 10% of my army left at a time, until my food production reached the point that it was high enough to feed the remaining troops. Greenmanofwow 20:38, January 31, 2010 (UTC)