The Iraq war might end like this:

•Iraqi Shiites, Sunnis, and Kurds uneasily share power and wealth in a single state. Sectarian violence, as well as terrorism linked to Al Qaeda, are diminished but not eliminated. Overseeing all this are perhaps 30,000 to 50,000 US troops, deployed in Iraq for years, maybe decades.

•Iraq is partitioned, accompanied by a return to the widespread sectarian violence of 2006 – times two.

Five years after the invasion of Iraq, those scenarios might be the best and worse cases that the United States now can aim for. One key to the outcome may be how long the US stays engaged in the expensive, drawn-out conflict.

From the point of view of the US, the Iraq war might be over when a president simply declares an endpoint. To an Iraqi, it might take much longer than that. Iraq today might be only at the midpoint, even the beginning, of a cycle of epic geopolitical change, say some analysts in a Monitor survey of experts in the region as well as in the US. For evidence, look at the Balkans, they say, which is still experiencing the geopolitical aftershocks of its mid-1990s wars.

"It will take the whole term of the next president to get this right," says Michael O'Hanlon, a Brookings Institution foreign-policy expert who advocates continuing surge-level US military efforts.

The Bush administration's vision of 2003 – that an Iraq freed of Saddam Hussein would be a peaceful hive of democracy, the Germany of the Middle East, and a source of strategic strength for the US – long ago proved wildly optimistic. It's been replaced by the knowledge that Iraq is a frail state, a source of strategic weakness, and a likely drain on US resources for some time to come.

On one basic point, the US invasion of Iraq has been wholly successful: It toppled Saddam Hussein. That may not seem as important today as it did at one time, given that the invasion also did not find any of his vaunted weapons of mass destruction, and that the unintended consequences of his removal have proved to be numerous.

But many of Mr. Hussein's neighbors considered him a source of instability. At least one US ally in the region remains grateful he is gone.

"Any Iraq will be better than Iraq under Saddam, because the Iraq of Saddam had the ability to threaten Israel," says Shlomo Brom, a senior fellow at Tel Aviv University's Institute for National Security Studies and former head of the Israeli Defense Force's Strategic Planning Division.

Of the misjudgments made by the US prior to its initiation of hostilities, however, one of the most profound was its error in predicting how Iraqi society would react once freed of Hussein's grip. Pushed by extremists, it split into ethnic and sectarian groupings. It turned out that few Iraqis – or, at least, not enough of them – had been waiting for the day they could found a Jeffersonian democracy.

"The main lesson of the invasion of Iraq is that you cannot engineer society," says Mr. Brom.

Sectarian competition will continue

Today, years of internecine warfare have taken their toll. Even under the best of circumstances, it appears inevitable that Sunnis, Shiites, and Kurds will compete for political and economic influence for years to come.

Within those sectarian and ethnic groupings various factions will vie for influence as well. At issue will be the nature of competition: ballots or bombs?

"People aren't going to be reconciled, there has been too much violence.... the question is can they work out a new set of arrangements," said Anthony Cordesman, a military expert at the Center for Strategic and International Studies, in a February briefing.

At this point in its experience in Iraq, the US is no longer trying to win a great victory, according to a range of analysts from around the world. It is simply trying to avoid defeat.

Much depends on the attitudes of the various groups toward basic questions of national identity. But even after all this time, the US may not really know whether the Kurds want their own state, whether Shiites will allow true Sunni participation in central government, and whether the Sunnis – Iraq's old ruling class – truly have given up dreams of reconquering the country.

"We don't really have a good fix on what the calculations of all these actors are," said Martin Indyk of the Brookings Institution in Washington during a January seminar on the future of Iraq.

The most crucial unknown: Is the current decline in sectarian violence a real trend – or are Sunnis and Shiites simply rearming and biding their time?

One bit of good news is that the country has not been physically partitioned into three sectarian cantons, as some predicted. At least, not yet.

The current situation is "semiseparation," says Mr. O'Hanlon. He estimates that about half of the possible ethnic cleansing that could occur in mixed neighborhoods, has.

Today Baghdad neighborhoods are separated by miles of security walls and blast barriers.

"If you get an [Iraqi] security force that is capable enough, get a couple of rounds of elections, more economic growth, there is a chance to take down those barriers," says O'Hanlon.

But it is only a chance, and a small one at that, he says. The worst-case scenario would be a return to the levels of violence of 2006 – times two. With such a resumption "at some point you would have complete ethnic cleansing," he says.

Iran ascends while US bogged down

Iran is one nation that seems poised to gain from Iraq's current situation. As Iraq's largest neighbor and a Shiite Muslim state, it has close ties with the current Shiite-dominated Iraqi government. Hussein and his Sunni-led regime, with whom Iran fought one of the bitterest regional wars of the late 20th century, is gone.

That does not mean Iran now wants Iraq to remain weak and unstable. To the contrary, Tehran has good reason to work for a stable and democratic Iraq, Iranian analysts say.

"In the next five years, Iraq should be united, with a Shiite government, without American troops, but with good relations with Iran and more secure," says Amir Mohebian, political editor of the conservative Resalat newspaper in Tehran.

At the moment, the US presence in Iraq is in Iran's interest, he says, to prevent radical Wahhabi Sunnis from helping Sunni insurgents form a Sunni state. But that does not mean Tehran needs to make things easy for US forces, he adds. Many US officials have accused Iran of passing lethal weaponry to an array of anti-US resistance groups.

Iran's strategic view is one of Tehran ascending, while the US remains bogged down in Iraq and hamstrung regionally by its pro-Israel policies.

"Now the US in Iraq is better for Iran, but [America] should not be secure, not be victorious," says Mr. Mohebian.

Turkey worries about Iraq disunity

Meanwhile, to Iraq's north, Turkey also sees a united Iraq as being in its own national interest.

If Iraq splits too much along sectarian lines, Turkey's own restive Kurdish minority might be tempted to join with northern Iraq's Kurds in a greater Kurdistan. That would be Ankara's worst-case scenario.

On the other hand, "the best scenario from the perspective of Turkey would be a territorially integral Iraq, one that is the same in terms of its current borders," says Faruk Logoglu, a former Turkish ambassador to the US who is president of the Eurasian Strategic Studies Center, a think tank based in Ankara that is considered close to the military.

Iraq is likely to adopt a federal system, with considerable power and authority delegated outside Baghdad. Turkey is fine with that, as long as Iraq's Kurds do not aid or shelter PKK Kurdish rebels.

There is already quite a bit of economic interaction between Turkey and northern Iraq, point out Turkish analysts.

"A stable Iraq would open opportunities for Turkey," says Lale Sariibrahimoglu, defense affairs columnist for Today's Zaman, a Turkish English-language daily. "Turkey would benefit as a transit route for Iraq's oil and natural gas resources."

Some analysts worry that a weak Iraq will become a regional battleground, with Saudi Arabia and other Sunni states rushing to bolster Sunni militias in a proxy war with Shiite Iran.

That's just one of the ways that Iraq's current problems might affect the larger region.

"The issue now, tragically, is not what happens in Iraq, but whether the damage is limited to Iraq or spreads to other countries in the region," says James Steinberg, dean of the Lyndon B. Johnson School of Public Affairs at the University of Texas.

The US, basically, is still going it alone in Iraq, says Professor Steinberg. It needs to do more to try and involve other countries and the United Nations, as it has in Afghanistan.

Iraqis: Time can heal divisions

Iraqi officials themselves say they simply need time – both to learn their own approach toward democracy and to develop Iraqi forces capable of securing their own country.

"Iraq is like a sheet that has been ripped. It will take time to reunite the fabric back together," says Gen. Naseer al-Abadi, deputy chief of staff for Iraq's armed forces.

The military surge has helped control violence, says General Abadi. Now the government needs to provide services and jobs.

That does not mean the war is over, he adds. The US and the Iraqi government are not even fighting an enemy, in the traditional sense.

"There is no center of gravity that you can hit to win the war," he says.

And the terrorists of Al Qaeda in Iraq might be a continuing problem, notes the Iraqi deputy chief of staff. The pool of willing Islamic militants in the Middle East is a deep one. Infiltration into Iraq is easy.

"Remnants will always be there," says Abadi.

How long will 'success' take?

Taking all these factors into account, success in Iraq at this point might be defined as a unified country that does not offer sanctuary to Islamic militants and is governed by a stable regime that is not under the influence of a hostile foreign power, such as Iran.

That, for example, is the bottom line of Andrew Krepinevich, a veteran Army planner and now president of the Center for Strategic and Budgetary Assessments.

Reaching this relatively stable state could take another three to five years – if it can be reached at all. Even then, the US might need to keep a substantial number of troops in the country – to keep Iraq's internal factions from going after one another and to protect the nation from its external enemies.

"A reasonable outcome would find something like 30,000 to 40,000 troops in Iraq for 25 to 50 years," says Dr. Krepinevich in an e-mail.

After all, the US has deployed troops in Germany and Japan for 63 years, and Korea for 57. Might Iraq, in the end, require a commensurate commitment?

• Contributing to this report were Monitor staffer Scott Peterson (Iran) and correspondents Sam Dagher (Iraq), Josh Mitnick (Israel), and Yigal Schleifer (Turkey).