Return of the mercenary

This Atlantic article explains why they are back in force:

McFate: The private military industry allows you to fight wars without having your own blood on the gambling table. And drones just do that as well. If you think about this as an arms-control issue, both [drones and private military companies] should be part of the same category, because they allow national governments to get involved in fighting without actually having citizens do it. And that creates moral hazard for policymakers, because it lowers the barriers of entry into conflict.