Um.. that never worked out.
One side will eventually win out, massacre the able men, fuck the opposed side's women and the women back home when they get back. After a few years of the coming-home-boom the population is much larger than before the war.
Sure the violence is dramatic, but much more effective solution to population control is education. If a couple has only two children, the population is stable. So if the child is able to take care of the parents in their old age, it becomes counter-productive to keep breeding (It is expensive to raise a child after all). Europe and Japan are now seeing decreasing population without massive scale plagues or slaughter.
Alas is it impossible to have all places on Earth to have a civilization level of that quality :-(