It's the other army. The private one, perhaps 160,000 strong in Iraq alone, armed, sometimes dangerous, often sloppy with tax dollars, and without which U.S. troops would represent a far less formidable force.

The coalition of willing contractors has swallowed more than $100 billion of U.S. spending on the Iraq war. More than 1,000 of its ranks have been killed since the 2003 invasion. Today, there is a U.S.-paid contractor — doing everything from manning a machine gun to cleaning toilets — for virtually every soldier tromping around the country.

Like never before in modern conflicts, military analysts say, war has become a corporate affair.

"We've gone too far in shipping out this work," said Peter Singer, who studies foreign policy and security issues at the Brookings Institution think tank. "It's created a big mess."

Yet without this civilian corps of gunmen, mechanics and pencil pushers, experts say, Washington would either need to send twice as many troops or settle for half the muscle.

With the outsourcing of so many war-fighting functions, the Pentagon risks a drop in the prestige and opportunity that military service has long promised. Many of the better jobs — ones that hone specialized skills in demand in the private sector — are being turned over to contractors.

A shootout this month involving Blackwater USA security guards left nearly a dozen Iraqi civilians dead and prompted the Baghdad government to revoke the firm's license. That, in turn, has raised anew concerns about whether armed squads move about Iraq answerable not to generals or governments, but only to their paymasters.

Still, gun-toting private security forces represent just a sliver of the massive force of contractors that free American troops for the work of combat.

By serving the meals, driving the trucks or consulting with the newly elected politicians, private firms handle many tasks that in previous wars might have tied up soldiers. In employing those contractors, the military can make more troops available for fighting.

"To some degree, having these companies makes it easier to go to war," said William Hartung, a military analyst at the New America Foundation. "Without massively increasing the size of the (uniformed) force, you couldn't do a conflict like Iraq without these guys."

The Pentagon is unsure of precisely how many private citizens are working in Iraq at Washington's behest, although estimates range from 125,000 to 180,000 people drawn from at least two dozen countries and working for roughly 300 companies. Americans can expect to make twice their U.S. wages in Iraq, much of it tax-free. Someone recruited from India or Indonesia can earn much more than they could make at home, but still pull in less than American minimum wage.

About 30,000 of those are employees of security companies. Even at its peak, the Vietnam War saw less than half as many contractors.

"This is the best-supported military operation in history," said Doug Brooks, a spokesman for the trade group International Peace Operations Association. "When soldiers come back from patrol, they don't have to clean the latrines. They only have to focus on the soldier part of their jobs."

On the ground in Iraq today, contractors are an inescapable presence. Pakistani laborers, sunburned engineers and burly security guards with rifles slung over their shoulders dominate the heavily fortified Green Zone in Baghdad and all but the most remote bases where troops are mustered.

Yet back in the U.S., contractors' role in the war is largely unseen. A recent study of 100,000 news media accounts of the Iraq war found mention of contractors in less than 0.25 percent of those stories.

Still, contractors make it possible to man the wars in Iraq and Afghanistan without dramatically increasing the size of the armed forces. Recruiting is already a struggle, and neither commanders in uniform nor politicians in Washington hold any enthusiasm for a draft. By delegating tasks to the private sector, Uncle Sam avoids making obligations of employment and veterans benefits to hundreds of thousands of people.