They have military-style weapons and duties. Many even have military-style body armor and crew cuts. An Iraqi could be forgiven for failing to understand that these men are guns for hire — not soldiers.

These hired guns, who number more than 15,000, generally prefer the term "private military contractors." They are a mixture of ex-military, mostly from Great Britain and the United States, but also from Australia, South Africa and elsewhere, including Fiji, Nepal and even Iraq. They serve many roles that are traditionally seen as the responsibility of soldiers, including guarding supply convoys for military contractors, training Iraqi soldiers and even supplying guards for Coalition Provisional Authority (search) Administrator L. Paul Bremer.

With the military having shrunk by one-third since the Cold War, the Pentagon has had to rely increasingly on contractors. Some industry insiders say well-run operations can boost military effectiveness and save money. But, company executives and industry analysts say that the private military business, which has ballooned since the Iraq war, is in need of better regulation. At the same time, after recent murders and kidnappings of security contractors, including an Italian who was executed on Wednesday, Democratic lawmakers are calling on the Pentagon to review the use of contractors.

Click here to read about the positions by Democratic lawmakers on security contractors.

"It would be a dangerous precedent if the United States allowed the presence of private armies operating outside the control of governmental authority and beholden only to those who pay them," a group of Democratic senators wrote to Defense Secretary Donald Rumsfeld last week, partly in response to the murder of four Blackwater U.S.A. (search) guards on March 31 in Fallujah.

Doug Brooks, president of International Peace Operations Association (search), and some in the military bristle at the suggestion that employees of private security companies are only driven by the bottom line.

"No one's going to go over there and risk getting 'Fallujah'd' if you don’t believe in the mission," Brooks said.

The military contractors are "all incredibly professional," Brooks said. That notwithstanding, he added that more regulation would be good for the industry. Currently, military contractors are not identified in a separate area of international law and hardly any countries have addressed these companies in their law codes.

"We'd like to see more international regulation. The real problem is the international community will not touch it," Brooks said. On the plus side, Brooks said, security companies depend on the U.S. government for the overwhelming majority of their contracts, and therefore, must comply with a certain standard of behavior if the government is to continue hiring them.

The industry is not regulated well enough, said David Claridge, managing director of the British company Janusian Security (search). "Most of the serious players are quite supportive of bringing in some degree of regulation. It is traditionally globally an unregulated industry except with a few exceptions. Iraq is forcing the industry to grow up and consider how the industry should be regulated."

Claridge said 180 companies are in Iraq. "Some of those are not providing people of adequate caliber, and if anything can be done to get those guys out of the marketplace, the better, because they're bringing everybody's reputation down."

Critics have seized on the origins of some of these men, who were previously employed in security roles by South Africa's apartheid government and in Soviet bloc countries. Media reports indicate that Blackwater is hiring Chileans who worked for former dictator Augusto Pinochet (search). Some of the companies have just grown too big, too quickly, Claridge said. They "are taking people that just don’t have the proper backgrounds to provide force protection services."

The philosophies of companies range widely. Blackwater's employees are frequently spotted in crew cuts, sunglasses and Blackwater T-shirts with guns drawn. Janusian guards grow their beards out, try to adapt to some of the local customs and live outside the protected Green Zone.

In the early 1990s, Congress decided that to cut down on the Pentagon's expenses, some of the non-"mission critical" functions should be farmed out to private companies. In fiscal year 2004, the Pentagon wants to privatize an additional 10,000 jobs.

Commenting on this phenomenon, Brooks said, "We have a leaner military than ever. The way they did that is by outsourcing a lot of the stuff they didn’t want to do." Brooks estimated that as a result, there are "probably 100,000 less soldiers in Iraq."

Some critics have noted that military contractors can be extremely costly, with annual salaries at $100,000 or more and some employees taking home $1,000 a day for short-term projects.

But Brooks said these companies are really saving the Pentagon money. A soldier may earn $35,000 or $40,000 a year, but the real cost to the Pentagon is $25,000 a month, Brooks said. Also the PMCs can get the job done with fewer men. "In every case you see that the private sector is 30 to 90 percent cheaper."

While the scale of military contractors may be new, working with private companies is old hat, said Jan Finegan, spokeswoman for Army Materiel Command (search). Hiring private contractors has been a military practice since the Civil War, Finegan said. "It frees up soldiers to do what soldiers normally do," she said, meaning fighting battles.

But these contractors are also filling roles traditionally played by soldiers. "This is the first time you’ve seen an extensive number of U.S. troops on the ground at the same time as private military personnel filling combat roles," said Brookings Institution (search) scholar Peter W. Singer.

"We're not willing to bear the political costs either to expand [the military] or bring in allies, so we're taking the short term, easy way out and turning it over to private entities," said Singer, author of a book on the industry "Corporate Warriors."

The fact that these companies are not regulated either by international law, national law or the Coalition Provisional Authority, troubles Singer. He said it is bad for the contractors because when they go missing or get in trouble, there is no defined role for the military in terms of aiding them. This danger has been highlighted in recent days with the frequent kidnappings.

"They also don’t fall under the code of military justice, and that opens up a legal gray zone that should be worrying to the public." But he was doubtful that any action would be taken soon because "there's been a lack of interest and political will behind it."