Very few were “blackwater types” i.e. former spec ops types.
Most were TCN’s slinging chow, some turned wrenches.
From the source:http://en.wikipedia.org/wiki/Private_military_company#PMCs_in_Iraq
PMCs supplied support to U.S. military bases throughout the Persian Gulf, from operating mess halls to providing security. They supplied armed guards at a U.S. Army base in Qatar, and they used live ammunition to train soldiers at Camp Doha in Kuwait. They maintained an array of weapons systems vital to the invasion of Iraq. They also provided bodyguards for VIPs, guard installations, and escort supply convoys from Kuwait. All these resources were called upon constantly.[8]