"Know the mission, protect your own, and prevent internal strife" - this is the advice of military and political experts for 200,000 US fighting men and women as they charge through the Arabian sands into an unstable nation of 24 million Iraqi citizens.
The experts contend that the history of 20th century US peacekeeping efforts can and should be instructive, if not necessarily encouraging.
President Bush has touted the possibility of Iraq evolving into an example of democracy for the Arab world. Senior Pentagon officials, however, say they will sustain existing institutions in Iraq - such as the security forces - by paying them to continue to help run a new nation.
Past mission to examine: Lebanon, 1982-1983.
When President Ronald Reagan sent 1,500 US marines to Beirut in September 1982, he called it "a mission of enabling the Lebanese government to restore full sovereignty over its capital, the essential precondition for extending its control over the entire country."
Dan Tschirgi, an American professor of political science at the American University of Cairo, says: "The precise mandate of the Marines was never clear. The US ground troops were there, in part, to help stabilize the Maronite leadership of President Amin Gemayel, but this angered opposing ethnic and religious groups."
A year later, the Marines had become "the enemy" of Muslim militant factions. On Oct. 23, 1983, Marine Sgt. Stephen Russell watched a smiling Muslim suicide bomber drive a five-ton dump truck at high speed through the gates of the US Marine compound near Beirut's international airport. The ensuing blast killed 241 American servicemen.
In "From Beirut to Jerusalem," author Thomas Friedman describes the Marines in Beirut as "good, milk-faced boys who stepped in the middle of a passion-filled conflict, of whose history they were totally innocent and whose venom they could not even imagine."
Professor Tschirgi, the author of "The American Search for Mideast Peace," says: "Just like what we are hearing today, senior American officials boasted in 1982 that Beirut would be 'our shining moment in the Middle East.' Instead, it was our time to become embroiled in the Lebanese quagmire and withdraw in utter humiliation. We hear National Security Adviser Condoleezza Rice taking the line that US forces will go in to occupy the country and that Iraq will turn out to be a democracy. I hope this is only empty rhetoric, because a serious US effort to attempt this is just begging for a catastrophe."
Taking a more optimistic view of current US goals, Joanna Spear of the King's College Centre for Defence Studies in London says she sees it as encouraging that once-isolationist Republican officials are talking openly about the great tasks of "nation building." She says that if the president and his top advisers are serious about approaching Iraq like the seven-year reconstruction of Japan, they might possibly succeed.
"On the other hand, they are also talking about using existing structures like the Iraqi Army to help in these tasks," she says. "Here you could run in the danger of perpetuating the inequalities and ethnic differences that already exist in Iraq. This wouldn't necessarily be a 'liberation' at all, and might turn US troops into the enemy."
Iraq has been a hotbed of interethnic strife for the past century. Middle East experts already predict that Shiite Muslims in the east and south of the vast country will seek quick revenge against members of Saddam Hussein's ruling Baath Party.
Past mission to examine: Bosnia, 1995-1996.
Some 45,000 US and NATO troops, along with international peacekeepers from 30 nations, entered a nation with about one-fifth of Iraq's population in a mission to divide feuding ethnic factions, keep the peace, and build institutions.
Capt. Mark Van Dyke, a senior adviser to the US NATO ground commander during the initial stages of the US-led mission, says: "For Iraq, one of the key concerns I already see emerging, especially in the Arab world, is to preserve existing borders. In Bosnia, the international community has tried to focus on creating a multiethnic country - what existed before the war there. We have also learned that this is difficult to achieve.
"If a US-led intervention proceeds in Iraq, we can take lessons from Bosnia on how to preserve the integrity of national borders," he adds.
"But Iraq also presents a much different scenario," Captain Van Dyke continues. "If an outside military force moves in to change a regime, you have to factor in possible collateral damage [civilian deaths and injuries]. If the invading force that enters the country is seen as the 'bad guys,' then they will face a huge challenge to take off their fighting hats and put on the peacemaking hats. Remember also, that in Bosnia, US forces entered with a broad multiethnic coalition that included Egypt and even Russia."
With Al Qaeda chief Osama bin Laden voicing his fresh determination to include Iraqis in his jihad against America, US forces will face daunting "force-protection" requirements - rules that require them to build up bombproof bunkers, travel in large numbers with heavy firepower, and keep an index finger always on the trigger.
Past mission to examine: Kosovo, 1999.
After a massive NATO bombing campaign, a UN-mandated coalition of 26 nations deployed 60,000 troops to preserve the peace and fragile ethnic mix.
Dr. Spear, who returned this week from a trip to Washington and meetings with senior US defense officials, says that projections by US Army Chief of Staff Eric Shinseki of the need for "several hundred thousand" US soldiers to keep the peace in Iraq are being taken seriously by senior US military officials, despite Defense Secretary Donald Rumsfeld's suggestion that the general's projections are too high.
"Senior US officers are not fooled," says Spear. "They consider the Iraq undertaking to be a massive and extraordinarily dangerous task, and they feel there has been an air of denial about the nature of the mission among civilian Bush appointees."
But one of the potential pitfalls in Iraq is the possibility that the force-protection requirements of the US Army will prevent them from performing their key tasks, especially preventing revenge killings.
"If your primary concern is protecting your own, it limits your ability to keep the peace," says Spear. "One major problem encountered in Kosovo, which could occur on a much greater scale in Iraq, is revenge killing."
Indeed, in the first several months of the NATO occupation, Kosovo Albanians, the ethnic group Western forces had been sent to protect, launched a spree of revenge murders against unarmed Serbs. The bloodshed stained the credibility of the NATO peacekeepers and added to an exodus of thousands of Serbian civilians.
"Iraq poses the possibility of major payback, and the international community needs to prevent this," says Spear. "One way to go about it is to plan to get a civilian police force in to stop the killing before it starts. For this, you might need a UN mandate."
Van Dyke, who now teaches university classes in international communications in Maryland, believes that the force-protection requirements in the Middle East will be much higher than usual because of the terror threat, but he says they can be overcome with increased numbers.
"Iraq will likely require higher numbers across the board," he says. "If you send out a patrol, you won't send one person, but several; you won't send out one weapon, but several. There are models to go by - equations, if you will - but you have to also factor in the terrorist threat and that means that the Balkans is not necessarily a good model for Iraq."