Well women are the rate limiting factor in having more men produced for war fodder.

It probably makes more sense to ban birth control at the same time men are required to die for the war machine as both would then be playing out their slavery-induced biological role in ensuring survival of the nation. That is if you're down with the whole slavery for war thing.

Biologically true, but probably not in practice. Do we think Ukraine will compell women to repopulate postwar? It won't happen.

Wouldn't make more sense instead of make conscription mandatory only for men, to make it mandatory for all childless people then?

Most actively wars are over long before the replacement rate starts to matter, and women that get pregnant or raise children will in all likelihood get an excemption from frontline duty.