The U.S. State Department is organizing a mercenary army to protect American interests in Iraq after U.S. troops have left (per treaty) at the end of next year. That agreement allows the U.S. State Department to maintain a few bases, and a security force of unspecified size. The State Department currently has a force of 2,700 security personnel in Iraq, most of them contractors (and most of them former U.S. military). But with the departure of all American troops by 2012, and the likelihood that Iraq will still be experiencing some violence, the State Department wants to expand its security force to 7,000, in order to deal with any emergencies. The expanded force would have MRAPs and helicopters, and personnel trained and experienced as "rapid reaction force" troops. The expanded force would be commanded by the State Department's existing security professionals. All this is nothing new.
For nearly a century, the State Department has had a security force, the Bureau of Diplomatic Security (BDS). The State Department even has about a hundred of their 1,500 BDS personnel trained to carry out commando type missions (the Mobile Security Deployment, or MSD). Members of MSD are trained to deal with kidnapping or terrorist threats at embassies. Most members are former military, and receive an additional six months training at a special State Department facility in Virginia. The skills they acquire are special operations type things, including how to drive a car in a combat situation. The MSD agents are mainly used to analyze dangerous situations, come up with a security plan, and carry out direct action (commando type stuff) if needed. Mainly, the MSD is a defensive organization, trained and equipped to protect diplomatic personnel under the most trying circumstances. That involves knowing how to evacuate an embassy under attack, usually with the help of U.S. Marines or SOCOM operatives.
The BDS also perform intelligence and investigative missions at American embassies. But mainly, they are security experts, doing what needs to be done, to keep the embassies safe. Even if that means running a small army.