merica's most important ally in the Iraq war may be a multinational force after all -- one composed of private military contractors. There is no official count of how many paid civilians are stationed in Iraq, but analysts estimate that the number could be as high as 20,000. (Britain, by comparison, has 11,000 troops in Iraq.) These contractors, often former military personnel from armies around the world, are employed not by any sovereign government but by multinational corporations.

Private military companies have been used in other recent wars, but not in such great numbers or so close to the battlefield. In Iraq, paid contractors don't just cook meals and build camps, as they did in the Vietnam War; they also perform guard duty, carry weapons, work on planning and logistics and train the new Iraqi military and police force.

According to Steve Schooner, co-director of the government procurement law program at George Washington University Law School, the Pentagon's outsourcing strategy helped win the initial stage of the war. ''Our ability to project technical superiority and overwhelming force in a short period of time at the outset of the Iraq war was driven by reliance on contractors, who can move very quickly,'' Schooner says.

The Pentagon's current overall strategy emphasizes a flexible, efficient, pared-down army equipped with the latest information technologies, many of which were developed in the private sector, not in military labs. Advocates of streamlining military operations say it's more efficient to subcontract the operation and maintenance of sophisticated systems to the companies that invented them, rather than have the military handle that itself. In Iraq, contractors are involved in maintaining and operating high-tech weapons systems -- including the F-117 stealth fighter and the M1A1 Abrams tank -- and operating unmanned drones.

Contractors have been killed and wounded in Iraq, although they aren't counted among the official tally of American deaths. When contractors are kidnapped, they aren't considered prisoners of war under the Geneva Convention, and their capture rarely attracts significant media attention. Deborah Avant, a political-science professor at George Washington University, says these facts can make it more politically expedient to deploy contractors than to deploy soldiers or reservists. ''It's easier for the government to do questionable things with contractors,'' she adds, ''because their deaths and kidnapping don't make headlines.''

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