This would necessitate an extensive discussion on what I feel is appropriate for a volunteer army, a conscripted army, and all the blends within. At the moment, I don't have the chance to give you the reply you'd deserve, but I don't want to leave you hanging. Suffice it to say that present day, any such humanitarian intervention should only be performed by a volunteer army.
That is, people should volunteer for the mission, and we shouldn't force anyone to do it if they don't want to. Now ideally, we'd live in a world where we've raised our children to be selfless and would volunteer regardless, which threatens the concept of free will/free choice. But that's why it's a more complex discussion.