Much is being made about the greater use of mercenaries in the American armed forces. The thousands of civilian technicians, and their civilian security forces, used by American troops in Iraq, is being portrayed by the mass media as somehow evil, or at least wrong headed. Actually, armed forces have used civilian contractors in combat zones for centuries. The first artillery crews were civilians, as the new weapons (in the 15th century) were too new and high tech for any existing soldiers to handle. Siege operations, a common form of warfare until about two centuries ago, was often conducted with hundreds, even thousands, of civilian contractors (civil engineers, craftsmen to build the siege engines and special equipment.) Every American army in the past century took with it thousands of civilian specialists to operate, install or maintain exotic new equipment. Eventually, soldiers would be trained to do the job of the civilians, as was the case with artillery and new types of electronic equipment. But the greater speed with which new technology is introduced today makes it impossible to have troops ready to take care of new equipment, at the same time that the new stuff can be used in a combat zone.
A lot of the civilian workers are not dealing with high tech, but with non-military work that would keep soldiers from doing what they were trained for. For thousands of years, this is what the camp followers did. The value of bringing civilians along for this sort of thing was rediscovered slowly after World War II. It works, as it has for over a hundred generations.
Providing security for a lot of these civilians, and some of the soldiers, using civilian security guards, is nothing new. Many American military bases in the United States are guarded by civilian guards. The use of private security forces in combat zones was actually pioneered by NGOs (Non-Governmental Organizations) operating in unstable areas. While local gunmen were usually hired, they were often supervised by retired Western combat experts (Special Forces and commandos were preferred). The NGOs dont have much choice, except on those rare occasions where they can convince the UN, or someone else with an army, to send in troops. The private security people do the job as good as professional soldiers, and have been doing so for decades.
Keep in mind that real mercenaries are freelance soldiers who will attack someone else for you. People who look after your new satellite communications gear, wash your clothes and guard your living quarters do not qualify.