Iraq's liberation has also generated new cultural, economic, and political ties among Shiite communities across the Middle East. Since 2003, hundreds of thousands of pilgrims, coming from countries ranging from Lebanon to Pakistan, have visited Najaf and other holy Shiite cities in Iraq, creating transnational networks of seminaries, mosques, and clerics that tie Iraq to every other Shiite community, including, most important, that of Iran. Pictures of Iran's supreme religious leader, Ayatollah Ali Khamenei, and the Lebanese cleric Muhammad Hussein Fadlallah (often referred to as Hezbollah's spiritual leader) are ubiquitous in Bahrain, for example, where open displays of Shiite piety have been on the rise and once-timid Shiite clerics now flaunt traditional robes and turbans. The Middle East that will emerge from the crucible of the Iraq war may not be more democratic, but it will definitely be more Shiite. ...

Stemming adversarial sectarian politics will require satisfying Shiite demands while placating Sunni anger and alleviating Sunni anxiety, in Iraq and throughout the region. This delicate balancing act will be central to Middle Eastern politics for the next decade. It will also redefine the region's relations with the United States. What the U.S. government sows in Iraq, it will reap in Bahrain, Lebanon, Saudi Arabia, and elsewhere in the Persian Gulf.

Yet the emerging Shiite revival need not be a source of concern for the United States, even though it has rattled some U.S. allies in the Middle East. In fact, it presents Washington with new opportunities to pursue its interests in the region. Building bridges with the region's Shiites could become the one clear achievement of Washington's tortured involvement in Iraq. Succeeding at that task, however, would mean engaging Iran, the country with the world's largest Shiite population and a growing regional power, which has a vast and intricate network of influence among the Shiites across the Middle East, most notably in Iraq. U.S.-Iranian relations today tend to center on nuclear issues and the militant rhetoric of Iran's leadership. But set against the backdrop of the war in Iraq, they also have direct implications for the political future of the Shiites and that of the Middle East itself. (my emphasis)

Washington failed to anticipate Iran's influence in Iraq largely because it has long misunderstood the complexity of the relations between the two countries, in particular the legacy of the war they fought during most of the 1980s. Much has been made of the fact, for example, that throughout that savage conflict - which claimed a million lives - Iraq's largely Shiite army resisted Iranian incursions into Iraqi territory, most notably during the siege of the Shiite city of Basra in 1982. But the war's legacy did not divide Iranian and Iraqi Shiites as U.S. planners thought; it pales before the memory of the anti-Shiite pogrom in Iraq that followed the failed uprising in 1991. Today, Iraqi Shiites worry far more about the Sunnis' domination than about Tehran's influence in Baghdad. (my emphasis)

Throughout the 1980s and after the anti-Shiite massacres of 1991, some 100,000 Iraqi Arab Shiites also took refuge in Iran. In the dark years of the 1990s, Iran alone gave Iraqi Shiites refuge and support. Since the Iraq war, many of these refugees have returned to Iraq; they can now be found working in schools, police stations, mosques, bazaars, courts, militias, and tribal councils from Baghdad to Basra, as well as in government. The repeated shuttling of Shiites between Iran and Iraq over the years has created numerous, layered connections between the two countries' Shiite communities. As a result, the Iraqi nationalism that the U.S. government hoped would serve as a bulwark against Iran has proved porous to Shiite identity in many ways. (my emphasis)

Granted, the legacy of the Iran-Iraq War, Iraqi nationalism, and, especially, ethnic differences between Arabs and Persians have historically caused much friction between Iran and Iraq. But these factors should not be overemphasized: ethnic antagonism cannot possibly be all-important when Iraq's supreme religious leader is Iranian and Iran's chief justice is Iraqi. Although ethnicity will continue to matter to Iranian-Iraqi relations, now that Saddam has fallen and the Shiites of Iraq have risen, it will likely be overshadowed by the complex, layered connections between the two countries' Shiite communities. (my emphasis)

So far, Tehran has favored a policy of controlled chaos in Iraq, as a way to keep the U.S. government bogged down and so dampen its enthusiasm for seeking regime change in Iran. This strategy makes the current situation in Iraq very different from that in Afghanistan after the fall of the Taliban in late 2001, when Iran worked with the United States to cobble together the government of Hamid Karzai. Tehran cooperated with Washington at the time largely because it needed to: its Persian-speaking and Shiite clients in Afghanistan made up only a minority of the population and were in no position to protect Iran's interests. Tehran's calculus in the aftermath of the Iraq war has been different. Not only do Iran's immediate interests not align with those of the United States, but Tehran's position in Iraq is stronger than it was in Afghanistan thanks to the majority status of Shiites in Iraq. Seeing the Bush doctrine proved wrong in Iraq would be an indirect way for Iran's leaders to discredit Washington's calls for regime change in Tehran. Their recent willingness to escalate tensions with Washington over Iran's nuclear activities suggests that they believe they have largely succeeded in this goal; Iran is now stronger relative to the United States than it was on the eve of the Iraq war.

And yet, in the longer term, U.S. and Iranian interests in Iraq may well converge. Both Washington and Tehran want lasting stability there: Washington, because it wants a reason to bail out; Tehran, because stability in its backyard would secure its position at home and its influence throughout the region. Iran has much to fear from a civil war in Iraq. The fighting could polarize the region and suck in Tehran, as well as spill over into the Arab, Baluchi, and Kurdish regions of Iran, where ethnic tensions have been rising. As former Iranian Deputy Foreign Minister Abbas Maleki has put it, chaos in Iraq "does not help Iranian national interest. If your neighbor's house is on fire, it means your home is also in danger." Clearly wary, Tehran has braced itself for greater troubles by appointing a majority of its provincial governors from the ranks of its security officials and Revolutionary Guard commanders. ...

After the fall of the Taliban in Afghanistan, the United States and Iran worked closely together to bring the Northern Alliance and its Shiite component into the mainstream political process. Washington and Tehran negotiated intensely on the sidelines of the Bonn conference on the future of Afghanistan, striking deals that helped ensure the early successes of the Karzai regime. The Bonn process promised to open a new chapter in the history of U.S.-Iranian relations. But at the time, Washington had little interest in further engaging a regime it believed it would soon overthrow. It missed an important opportunity then.( my emphasis)

But if Washington and Tehran are unable to find common ground -- and the constitutional negotiations fail -- the consequences would be dire. At best, Iraq would go into convulsions; at worst, it would descend into full-fledged civil war. And if Iraq were to collapse, its fate would most likely be decided by a regional war. Iran, Turkey, and Iraq's Arab neighbors would likely enter the fray to protect their interests and scramble for the scraps of Iraq. The major front would be essentially the same as that during the Iran-Iraq War, only two hundred miles further to the west: it would follow the line, running through Baghdad, that separates the predominantly Shiite regions of Iraq from the predominantly Sunni ones. Iran and the countries that supported it in the 1980s would likely back the Shiites; the countries that supported Iraq would likely back the Sunnis.

Iraq is sometimes compared to Vietnam in the early 1970s or Yugoslavia in the late 1980s, but a more relevant - and more sobering - precedent may be British India in 1947. There was no civil war in India, no organized militias, no centrally orchestrated ethnic cleansing, no battle lines, and no conflict over territory. Yet millions of people died or became refugees. British India's professional army was sliced along [communal] lines as the country was partitioned into Hindu-majority and Muslim-majority regions. Unable to either bridge the widening chasm between both groups or control the violence, the British colonial administrators were forced to beat a hasty retreat. As in Iraq today, the problem in India then lay with a minority that believed in its own manifest destiny to rule and demanded, in exchange for embracing the political process, concessions from an unyielding majority. The pervasive sectarian violence and ethnic cleansing plaguing Iraq today are ominous reminders of what happened in India some 60 years ago. They may also be a worse omen: if the situation in Iraq deteriorates further, the whole Middle East would be at risk of a sectarian conflict between Shiites and Sunnis. (my emphasis)