Since the Pentagon has decided to cut the US Army by 10 combat brigades, it might be a good idea to brush up on your military mercenary knowledge.
Here's a quick link to the 9 largest private armies in the world. Stratrisks!
Its a time honored tradition that governments have done for centuries. It fell out of style with the massive national armies of the Napoleonic era through the 1980s, but since the fall of the Soviet Union, its back in style. Mercs have been commanding an ever larger role on the battle field, both behind and on the lines.
Sadly . . .