During the Vietnam War, the United States insisted that if South Vietnam fell, its neighbors would tumble to communism one after another. Decades later, Washington is gambling on a new domino theory -- one in which a war to liberate Iraq unleashes broad change, including a wave of democracy in the Middle East.
It is a grand vision that offers tantalizing rewards, but also includes huge risks.
By contemplating a new kind of war -- a preemptive assault to oust Saddam Hussein in the name of protecting Americans from rogue nations and terrorists -- the Bush administration also aims to bring peace and stability to the Middle East, end terrorism and ensure Israel's survival and the free flow of oil.
Its willingness to force its vision on leaders across the Middle East has sparked angst and resentment. Widely discussed plans for a postwar occupation have only heightened the alienation. America's friends, including France and Germany, have reacted with dismay and diplomatic roadblocks.
The Arab response could be far more intense. In a part of the world dominated for centuries by outside empires, where people already are angry about U.S. support for Israel, experts say Washington is on a dangerous course.
They warn that the dominoes could fall badly wrong, threatening governments that are friendly to the United States, ushering in a new wave of anti-Americanism and triggering another convulsion of terrorism.
It is a risk the Bush administration appears willing to take. Convinced that a quick and successful war to oust Hussein can begin the desired change, Washington has told allies -- and the United Nations -- that it intends to do what it wants, and is prepared to do it with or without their help.
"By removing Saddam Hussein the U.S. signals to the rest of the world the length they will go to achieve their core foreign policy goals," said Toby Dodge, senior research fellow at the University of Warwick in England. "That is what the Bush doctrine is about. That is what this war is about."
Analysts, including the authors of a classified State Department report leaked in Washington last week, doubt that ousting Hussein will foster democracy in the region.
And however logical and well-meaning the administration's vision for the Middle East may seem to Americans, no matter how strong the hopes are for a decisive war and a brief occupation, the reaction in large parts of the Arab world could hardly be more different. For many Arabs, the U.S. action is proof that they have landed in the crosshairs of Washington's war on terrorism.
They regard the United States as a new colonial power that will further strengthen Israel and strip the Palestinians of any hope for an independent and viable state. They believe America will impose its own vision of good governance on a region that has never accepted Western democracy as the best way to govern, then promote its religion and its culture, and eventually loot the region's oil and gas reserves.
"I believe they want to change regimes all over the region -- not for our sake, but for theirs," said Bassam Noh, a 21-year-old political science student at Cairo's American University, who until recently was not politically active.
Many here say they fear that an attack on Iraq may well achieve what Osama bin Laden could only dream about: It will radicalize a generation of young people, who account for more than half the Arab population. It will not only persuade them that Bin Laden was right -- that Bush is at the head of a new Christian crusade against the Islamic world -- but also that their leaders are impotent and concerned primarily with self-preservation.
That will empower Islamists from Morocco to Kuwait, inspire terrorists and undermine many governments -- including U.S. allies -- that already struggle for legitimacy.
Arabs worry what America might do next: Force reform in Iran? Pressure Saudi Arabia to overhaul its religious-based political system? Impose a solution of the Israeli-Palestinian conflict with no viable Palestine?
A poll of people in six Middle East countries released in mid-March indicated that the vast majority expected a U.S.-led attack on Iraq to lead to greater instability and more terrorism, and hurt chances for a settlement to the Israeli-Palestinian conflict.
Washington's shifting explanations to justify war have only deepened Arab suspicion. The U.S. has variously cited the need to eliminate Iraq's suspected weapons of mass destruction, Hussein's abysmal human rights record, and his alleged connections to Bin Laden's terror network as reasons to justify the confrontation.
But even at their most benevolent, Bush's explanations have been viewed skeptically.
"In a free Iraq, there will be no more wars of aggression against your neighbors, no more poison factories, no more executions of dissidents, no more torture chambers and rape rooms," Bush said in his speech Monday that imposed a 48-hour deadline for Hussein to leave Iraq.
He added: "We believe the Iraqi people are deserving and capable of human liberty, and when the dictator has departed, they can set an example to all the Middle East of a vital and peaceful and self-governing nation."
Baghat Kouhry, 63, a political scientist and author in Cairo, likens Washington's rhetoric to the British justification for ruling Egypt as a protectorate in the early part of the 20th century.
"People will resent what is taking place," he said.
Much of Arab identity has been forged by hundreds of years of imposed subservience -- a fact underscored by the Arab response to Bush's description of America's war against terrorism as a "crusade." The fury that spread throughout the Arab world stemmed from the perceived link to the religious march of Christians into the Middle East that began in the 11th century.
The thought of an outside power sending a military force into the region, even to attack a leader as widely reviled as Hussein, also awakens this region's collective memory of later invasions. Ottoman Turks swept across the Arab world in the 16th century and held sway over a vast and culturally diverse group of people for hundreds of years.
As the empire frayed, finally collapsing at the end of World War I, France and Britain carved up much of what is the modern Arab world. They established borders and created states, imposed leaders and divided up spheres of influence.
Arabs are worried that history will repeat itself.
"In the U.S., they are thinking it will be a speedy operation and the Iraqis will welcome it," said Abdel Moneim Said, director of the Al Ahram Center for Political and Strategic Studies, a government-funded think tank in Egypt. "That is not the perception here. The political and military evaluation is it will go sour, it will go longer and it will have a negative spillover effect on the rest of the region."
Any calculation of the stakes of a new Iraq war begins with the issue that has shaped the Arab world for generations: the Israeli-Palestinian conflict. Though the Arab community is divided by politics and local customs, it is united by a universal connection, one inspired by a common language and -- for the overwhelming majority -- a common religion, cemented by an "us against them" outlook.
"I can remember the day in school a teacher said to me, 'What are you?' " recalled Talla McIlvain, who grew up in Jordan with an American mother and Jordanian father. "I responded automatically, 'I am an Arab.' And the teacher said: 'Good for you. We are all Arabs first.' "
So U.S. support for Israel against the Palestinians, who are Arabs, automatically makes America the enemy. It is unlikely anyone on an Arab street will give the United States the benefit of the doubt in dealing with Iraq's Arabs.
Even when Bush commits the United States to solving the Israeli-Palestinian conflict, as he did again March 14 as the White House scrambled to bring the Iraq issue to a head, the Arab community is suspicious. It is widely believed that the United States will impose a humiliating cease-fire, relegating the Palestinians to a bastardized state forever under the thumb of the Israeli military power.
"I think [Washington] reckons that the Palestinians have lost their chance for a state," said Rosemary Hollis, director of Middle East studies at the Royal Institute for International Affairs in London. "They think they had their chance and lost it."
If Iraq is sidelined, Egypt would be the only Arab country left with the military power to possibly take on Israel. That could happen only if Cairo violated its peace treaty with the Israelis, which it has gone to great lengths to abide by despite its anger about Israel's actions in the West Bank and Gaza Strip.
Iraq may have been tamed after the 1991 Persian Gulf War, but it still had the largest military in the region.
"Americans will be victorious, and I think their demands on the Palestinians, dismantling the infrastructure of Hamas and Jihad, will be asking for a kind of Palestinian civil war," said Moneim Said of the Al Ahram center. "I assume the Palestinians will escalate their struggle; that will be part of the chaos to take place."
This is where the dominoes might begin to fall.
With Iraq changed, analysts believe that the United States would be in a stronger position to influence neighboring Syria, which provides logistical and financial support to the main militias fighting Israel -- including Islamic Jihad, Hamas and Lebanon-based Hezbollah.
Though Syria is a nation strong on Arab nationalist rhetoric and aggressive in its support of proxy armies, it is reluctant to take up a fight head-on. Syria helps fuel border battles with Hezbollah and hosts the offices of radical Palestinian groups that stage suicide bombings. But it has done nothing to promote an insurgency in the Golan Heights, which Israel captured in the 1967 Middle East War and later annexed.
The United States would also regard change in Iraq's eastern neighbor, Iran, as a positive development.
Iranian hard-liners may fear that they are next, and that could lead them to reconsider their severest anti-Israeli activity, as well as efforts at nuclear proliferation.
"The impact of war could very well accelerate the internal process of change in Iran," said Davoud Bavand, an analyst and former diplomat under the shah's regime.
But Islamic governments unfriendly to the United States are not the only ones that would face pressure from the streets. Although most governments can expect some degree of civil disorder, those that are closest to the U.S. are likely to face the greatest challenges, observers said.
Poverty is rampant across the region, political freedoms are limited or nonexistent, and the viability of governments is ensured by secret police, emergency laws and ironfisted policies.
Kuwait, which was liberated during the Gulf War by a U.S.-led coalition, has already experienced a surge in terror-related actions, which could spike in the event of a new war and undermine an economy built on the labor and skills of foreigners. Saudi Arabia could also find itself the target of a terror campaign as radicals adopt the Iraqi cause to pursue their aim of bringing down the monarchy.
Jordan, which has close economic and social ties with Iraq, faces a fiscal crisis if its deeply discounted Iraqi oil stops flowing, and an internal crisis if crowds take to the streets.
And Egypt, considered the most stable of U.S. allies in the region, faces a collapse in tourism, the repatriation of 300,000 expatriate workers in Iraq and the loss of Suez Canal revenue. Estimates put Egypt's loss in the first year at up to $10 billion.
Economic hardship and very young populations in many countries create big pools of angry, disenfranchised people with no outlet for venting their views.
"I hate the Americans -- the government and the people as well," said Dina Ahmed, 18, a freshman studying to be a tour guide at Ain Shams University in Cairo. "They can change their government's policy, but they don't do that. They hate us."
Because many Arab governments have virtually shut down any political opposition, the only groups that provide an alternative are religious-based.
In Egypt, the Muslim Brotherhood is banned but remains a powerful opposition force. More than 100,000 Egyptians defied state security recently to attend a funeral for Mustafa Mashour, the organization's longtime leader.
"With the occupation of Iraq, the streets will explode. The left is too marginal to lead this, so the Islamists will try to provide the leadership," said Hassanein Keshk, a sociologist at Egypt's National Research Center, a government-funded think tank. "If the protests are sustained and if the Muslim Brotherhood tries to ride the wave, we could even experience a military coup."
The story of Sayyed Aboud Hassanein illustrates one of the reasons so many Arab leaders worry. He grew up in a small Egyptian village north of Cairo. He liked to write short stories about love and life, and worked with his father selling clothing in the streets of his village.
In November 2002, when he was 21 years old, he strapped on an explosive belt, rushed toward an Israeli military outpost in the Gaza Strip and blew himself up.
The young man was not a member of a political organization and his family and friends say he was not extremely religious. But his decision now has many people asking how many more Hassaneins are out there.
"Clearly this would be a formative experience for someone 14 to 18 now," said Ellen Laipson, an Iraq expert and former vice chairman of the National Intelligence Council. "This would be one of the most important political events in their life."
She said they could turn to Bin Laden as a charismatic figure offering an alternative.
Even America's many critics say there are some ways for the United States to minimize the effects of war.
It would have to prevent Iraq from destroying its oil wells or the wells of Kuwait to prevent skyrocketing oil prices, which would hurt industrialized and developing nations alike.
But more fundamental, the United States must avoid killing large numbers of civilians and show that it was correct about Iraq. It must prove that Iraq was hiding weapons of mass destruction, that the Iraqi people view the invasion as a liberation, that it is sincere in its efforts to build a viable, independent and democratic state -- and that it is not seeking to dominate the region.
"We are likely to be forgiven for the war if we do well at nation-building," said Anthony Cordesman, a military analyst based in Washington. "If we are seen as carrying out an imperialist role, it will be deeply damaging.... The question here is not so much can we win the war -- we probably can -- but is whether we can win the peace."