WASHINGTON — Picture U.S. troops advancing up the monumentally wide boulevards of central Baghdad, greeted joyously by throngs of Iraqis who have just overthrown Saddam Hussein and his dictatorship.
What then? Getting rid of Saddam — as President Bush has pledged to do — may not be easy. But it could be a walk in the park compared with what follows, according to experts on Iraq, U.S. officials and Iraqi dissidents.
In the worst-case scenario, Iraq's fractious ethnic groups could try to break off their own mini-states, trapping American combat forces in the middle of a civil war. Those repressed under Saddam's vicious police state might engage in a bloody round of score settling. Even in the best case, U.S. troops and diplomats could be stuck in Iraq for years, trying to teach the finer points of democracy to a nation that has never known it.
Sen. Joseph Biden, D-Del., said in an interview last week that he told Bush, "There is a reason that your father stopped and did not go for Baghdad" after the 1991 Persian Gulf War. "And that was having to stay for at least five years."
Biden's Senate Foreign Relations Committee opens hearings today on Bush's Iraq policy as the White House and Pentagon move forward with planning to oust Saddam and destroy his weapons of mass destruction.
Bush so far has not offered a clear vision of what he foresees for Iraq's 23 million people after Saddam is gone, U.S. and Iraqi observers say. Doing so now is the key to avoiding chaos later, they say, and could even prompt Iraqis to take matters into their own hands, making an American invasion unnecessary.
"The United States has to be thinking not only of the military question, but also of the political question," said Iraqi dissident Kanan Makiya, author of "Republic of Fear," a profile of Saddam's Iraq.
With Iraqi opposition groups, the U.S. government should "work out a vision and state it up front of military operations," said Makiya, a professor of Middle East studies at Brandeis University. "That will be enormously positive. It will minimize the disruption."
"New political leadership (in Iraq) is critical, and I don't see that much thinking yet has gone into this problem," said Iraq scholar Phebe Marr, who will testify at Wednesday's hearing.
Modern Iraq is an artificial nation, an amalgam of Shiite and Sunni Muslims, Kurds and a smattering of other ethnic groups that British colonialists stitched together in 1921 from three provinces of the old Ottoman Empire.
Bush might want to heed the lesson of Gertrude Bell, the eccentric British Arabist who, along with T.E. Lawrence, installed King Faisal on Iraq's throne with the backing of Britain's military. Britain left, Faisal's grandson was assassinated in 1958 and Iraq has been ruled by a series of strongmen ever since.
Iraq's exiled opposition — Saddam kills internal political opponents, real and imagined — reflects the country's divisions. Its leaders spend more energy bickering among themselves than trying to overthrow the regime.
Top State and Defense department officials, who themselves have argued bitterly over Iraq policy, are due to meet with opposition leaders Aug. 9 in yet another effort to get the exiles to work together.
The State Department also has been holding a series of workshops for expatriate Iraqis on such things as an independent judiciary and a modern education system.
A White House official, speaking on condition of anonymity, said top Bush aides had spent a lot of time discussing a post-Saddam Iraq and how U.S. strategy for ousting the Iraqi leader, whether militarily or otherwise, would shape the country's future.
As part of a "regime change" strategy, "you have to think about what happens after the regime has changed," the official said.
Some analysts argue that the dangers of Iraq fragmenting or disintegrating into chaos are exaggerated.
Unlike Afghanistan, Iraq is not poor. It has huge oil reserves, a modern if decaying infrastructure and a middle class that remembers when Iraq was a modernizing country in the 1970s and '80s.
The resources that have helped Saddam develop chemical, biological and nuclear weapons and make Iraq into a threat "can be turned into advantages," Makiya said.
Michael Rubin, a visiting scholar at the American Enterprise Institute, a conservative policy research center in Washington, said the breakup of Iraq was unlikely.
Ethnic Kurds in the northern part of the country already have a federal system, and it is largely free from Baghdad's control, said Rubin, who has lived in that region. Shiite Muslims, while they have co-religionists in neighboring Iran, are unlikely to try to break free and join that country, he said. Iraq's Shiites are Arabs; Iranians are not.
After Saddam leaves the scene, any real fighting will be in and around Baghdad and will last only a day or two, Rubin said. "It's just going to take a little while for a new status quo to emerge," he said.
But who will control Iraq after that?
One possibility is the U.S.-backed opposition groups. But with little support in Iraq, they probably will need military and economic support from Washington for years, experts say.
An internal coup might produce a military strongman not altogether different from Saddam.
"A coup or a change from inside the regime might not bring sufficient change in direction or policy and is less likely to be democratic," Marr said.
Some, such as Makiya, argue for bringing democracy to Iraq. But David Mack, a former State Department official and vice president of the Washington-based Middle East Institute, a research organization, said Bush should keep his goals more modest.
The president should aim for a government that is at peace with its neighbors and agrees to give up weapons of mass destruction, Mack said.
While he favors regime change, "You need a massive commitment of resources and national will to ensure you succeed," he said. "Secondly, I think we're talking occupation here for years."
Jonathan S. Landay in Washington contributed to this article.