Nobody said the war in Iraq was going to be easy — but the stress of a war zone, a lean military force and a growing contingent of private contractors is fueling tensions as the nation rebuilds.

More than two years after U.S.-led forces ousted Saddam Hussein, signs of conflict have appeared. One contractor claims a “vicious” military officer mistreated him when he was forced to move out of Baghdad’s “Green Zone,” while a group of 16 contractors say they were treated like terrorists while detained for three days by fellow Americans.

Some experts, although they were not able to speak specifically to the incidents mentioned, said that such reports may be the result of a combination of the rigors of the potentially deadly job, being away from their families for so long and an inability to see any real end in their mission.

[Editor's Note: This is the third in a four-part series on tensions between American contractors working in Iraq and the U.S. military. To read part I, click here. To read part II, click here.]

"In my experience, the relationship between the contractors and the military has been fairly good ... contractors, being mostly former military themselves, usually do whatever they can for the military guys. By and large, the quality of service provided has been excellent," said Col. Christopher Holshek, an Army Reserve officer who commanded a battalion in Iraq.

But "tensions are high over there regardless, because it's a very dangerous area," Holshek said, adding that many in the military have probably been deployed for a second or third time to Iraq. "It's not any easier for the contractors, either, because they're in a very dangerous situation. They're extremely vulnerable. ... Sooner or later, the stress has got to manifest itself somewhere."

Situations such as the ones alleged by the contractors in question could be a result of poor discipline or a breakdown in the chain of command, or simply excess stress.

"Bad behavior can't be excused," Holshek said. "Still, you need to look beyond that and say, 'What's happening behind that situation that's causing this kind of abnormality?'"

Along with the so-called "shadow army" — the estimated 20,000 private security contractors in Iraq who are securing convoys, high-level officials and infrastructures — are another 100,000 or so contractors working with Iraqis to help them rebuild a country worn down by over 30 years of conflict.

They may get paid more than military men and women, on average, but these contractors say they're also waving the red, white and blue while serving in Iraq. They say they’re there because they felt a higher calling of duty, patriotism and love of country.

'Everybody's Getting Frustrated'

FOXNews.com has spoken to several contractors and their families who, while completely supportive of the mission at hand and the military men and women carrying it out, say they have had run-ins with a handful of military personnel in Iraq that took them by surprise.

Darla Russell's husband, a former military man and current security contractor in Iraq, encountered one such incident with a Marine officer about a month ago. The officer allegedly kicked her husband and his colleagues out of their living and working area, saying, 'We don't like contractors.'

“[Contractors are] all over there for one thing, and if the contractors weren't over there, a lot of the stuff they're [the military] doing wouldn't get done. In my view, they all need to stand together,” Russell said.

Many military officials and contractors say their working relationship is productive and great 99 percent of the time, but they acknowledge that tensions arise in the midst of war.

The reported problems are not just of the military variety. Some contractors have also come under scrutiny for their actions.

The Pentagon is investigating American firm Custer Battles for allegedly cheating the U.S. government out of tens of millions of dollars during the chaotic months following the Iraq invasion. In September 2004, the military banned the company and 15 of its subsidiaries and officials from obtaining government contracts while the criminal probe proceeds.

Custer Battles employees have also been accused of firing on unarmed Iraqi civilians, of using fake offshore companies to pad invoices by as much as 400 percent and of using forgery and fraud to bilk the American government. Two former associates have filed a federal whistleblower suit, accusing top managers of swindling at least $50 million.

But just as contractors with complaints against a few in the military are not generalizing the entire armed forces from the experiences with a few, they say incidents like that of Custer Battles shouldn't be representative of the entire contracting community in Iraq.

"I think it's just everybody's getting frustrated, we've been there three years and every time we think we're getting ahead, we get set back," said Eric Shaver, a former contractor who worked in Iraq with Zapata Engineering and was one of 16 American contractors with that company who were detained by Marines in Fallujah for three days, during which they claim they were verbally and physically abused.

"I think myself, including a lot of these soldiers, are starting to see, you know, we're not getting anywhere," he added.

Counting Dollars

Many private contractors have said some tension arises when military personnel learn how much money they make.

Guards for private security firms can typically earn between $400 and $600 per day. Guards employed by Blackwater, a high-profile American company that guarded former CPA chief Paul Bremer, are sometimes paid up to $1,000 per day. Many companies like Halliburton subsidiary Kellogg, Brown and Root offer $80,000 to $100,000 a year. Some companies offer more for what they call "hazardous duty."

For the military, one's rank and years of service determines the amount of basic pay received. According to the military pay and benefits Web site sponsored by the Office of the Under Secretary of Defense for Personnel and Readiness, commissioned officers with six years of service, for example, can earn anywhere from just under $3,000 a month to more than $8,000 a month. Enlisted members in the service that long can earn as little as $1,235 a month up to just under $3,000 a month.

But life insurance policies for contractors are not usually as generous as their paychecks, or as solid. When a member of the U.S. military is killed, the soldier's family is guaranteed life insurance and death benefits.

Contractors, many of whom go to Iraq voluntarily, are often on their own to find housing and security for their workers in a region that's plagued with armed insurgents, homicide bombers and anti-American sentiment. The military comes to the aid of contractors when it can and, likewise, the contractors do the same for their military friends. But that can't always be counted on in either case.

"When they [contractors] go out on convoys, they have no military forces to back them up on their runs but they work directly with a lot of the Iraqis to help them build back their countries, the power plants, the schools, the roads and everything like that," said Jana Crowder, whose husband is a private contractor helping with reconstruction in Iraq.

Added Shaver: "when you work out there, if you don't have close military support … if you don't have your stuff together out there, you're basically on a suicide mission."

A Smaller Military

A bigger paycheck and a civilian job may seem more attractive to many in the military, particularly as they continue fighting an insurgency that clearly doesn't want them there, have their lives threatened every day in scorching heat and don't want to be deployed again.

Many contractors have talked about how, when working in Iraq, they have been approached by military men and women about potential employment opportunities in the private sector.

Some in the military say that while they need contractors in the field, this is one reason for some strain.

"I work with contractors on a daily — and sometimes hourly — basis. I can tell you these contractors are as patriotic as the soldiers in my battalion. I have a superb relationship with the contractors and we work together well," said Lt. Col. Robert Roth. Roth is commander of U.S. military security forces in and around the Green Zone, otherwise known as the "international zone" in Baghdad.

"I am impressed by the professionalism and work ethic of the contractors here in Iraq," he told FOXNews.com in a recent e-mail exchange.

But, he added: "My biggest problem is when the contractors approach my soldiers and offer them employment after their enlistment is complete."

There are about 140,000 U.S. troops in Iraq, what many consider to be a small number of people to do a massive job.

While some have criticized the Bush administration and the Pentagon for essentially trying to run this war on the cheap, defenders have said a smaller contingent will force Iraqis to do more for themselves, and in a shorter amount of time, so America's troops can come home.

"Sending more Americans would undermine our strategy of encouraging Iraqis to take the lead in this fight," President Bush said in a national address Tuesday night. "And sending more Americans would suggest that we intend to stay forever — when we are in fact working for the day when Iraq can defend itself and we can leave."

Before Bush took office, the United States for a decade tried to downsize the U.S. military in an effort to modernize a fighting force for the post-Cold War era. While this may have had benefits, some experts agree that a smaller force may be taking its toll on the troops in Iraq.

"I do think you have to address this morale issue very seriously," said Michael O'Hanlon, a senior fellow of foreign policy studies at The Brookings Institution.

For troops already in the field where retention is the issue, he said, "The issue is partly the danger but probably even more, the time away from home and that obviously is tied directly to Iraq."

The Army on Thursday said it exceeded its monthly nationwide recruiting goals for June, putting a halt to the four-month slide it had experienced. Recruiters hope to make up the deficit during the last three months of the fiscal year. But this comes on top of other news that suggests an increasing number of parents are dissuading their kids from entering the military out of fear of being sent to battle.

"I do not think the problem is permanent, I think the problem is definitely tied to Iraq and I think that's true across the board. ... I don't think parents are against their kids being in the military, parents are against their kids getting killed," O'Hanlon said.

"I think after this operation has concluded, unless something bad happens [in Iran, North Korea or elsewhere] ... we're not likely to have the kind of casualty problems we're having in the future as we're having right now" and recruitment will be easier, he said.

"No matter how you look at it, it's primarily an Iraq-specific issue. ... I think it's quite serious, [and] getting through just a couple of years at this intensity" isn't going to be easy, O'Hanlon added.

Check out FOXNews.com next week for the final part of the series, focusing on how family members of contractors deal with the stress of having a loved one in Iraq.