More relevantly, in a modern war you want experts. Even grunts need to know a lot to be effective, they have drilled and drilled until they react correctly without thinking about it - and somebody in charge of a handful of them needs to know how to use their skills to achieve larger strategic goals which then trickle up.

Needing to use a draft is a bad sign - the more of your soldiers are volunteers the better quality you'll get out of that.

Or the privileged kids are placed in safe deployments.

cue Creedence - Fortunate Son

Or officer commissions purchased.