I was just think about this because of something GoftheJ said. It may be a good idea to tie your population's support for a war to how many lives have been lost in it. This would deter people from mindlessly rushing other people and increase the value of each unit to the player. Certain other society types might find such deaths a positive.
Real life adds complications.
Like lynch mobs showing up at your government mansion. Morale should decrease the further away your units are from a friendly base, and it should decrease as casualties are taken. Martyrs die to defend their homes and rally the rest of the population into a killing frenzy. But if the populus doesn't agree with the war you get hippies. I don't think inot distance should lower morale.