In the last half century conscription has fallen out of favor, but volunteer troops are too expensive to be used for a lot of support jobs, so more and more of these chores are contracted out to civilians. Even if you're in Iraq or Afghanistan you often won't even notice a lot of the contractor civilians. They often wear army combat uniforms, without any rank insignia. Some are armed. They work for the army without being in the army. But the truth of the situation is that the military has been going back to the past to find the future.
Mass conscription reduced this longstanding practice. Now it is growing.
The Left used to hate "mercenaries." Now they ignore them.
This is something I addressed in my one and only compilation of blog posts on private warfare trends (and only 99 cents!)