It looks increasingly as if President Bush may have been off by 74 years in his assessment of Iraq. By deposing the dictatorship of Saddam Hussein, Bush assumed he would bring Iraq to its 1787 moment -- the crafting of a democratic constitution, the birth of a unified republic. Instead, he seems to have brought Iraq to the brink of its own 1861 -- the moment of national dissolution.

No, I don't mean that Iraq is on the verge of all-out civil war, though that's a possibility that can't be dismissed. But the nation does appear on the verge of a catastrophic failure to cohere. The more the National Assembly deliberates on the fundamentals of a new order, the larger the differences that divide the nation's three sub-groups appear to be.

It's not the small stuff that they're sweating in Baghdad. They can't agree on whether the new Iraq should be a federation, with a largely autonomous Shiite south and Kurdish north, or a more unified state, which the Sunnis prefer. They can't agree on just how Islamic the new republic should be, and whether the leading Shiite clergy should be above the dictates of mere national law. They can't agree on whether religious or state courts should hold sway in Shiite-dominated regions, or even the nation as a whole; they can't agree on the rights of women. They can't agree on the division of oil revenue among the three groups. They can't agree on whether there should be a Kurdish right to secede enshrined in the constitution.

In short, they can't agree on the fundamentals of what their new nation should be. And the more they deliberate, the less they agree on.

These are not unanticipated disagreements. Before the war began, many critics of Bush's rush to war, including some in the State Department and the CIA, argued that while overthrowing Hussein would be relatively easy, building a post-Hussein Iraq would be devilishly difficult. Bush's defenders argued that Iraq was a largely secular land in which many Shiites, Sunnis and Kurds lived together amicably and frequently intermarried. They weren't entirely wrong, but one could have made the same argument about Tito's Yugoslavia before it dissolved into genocidal violence. They missed the deep resentments and the growing fundamentalism that Hussein's thugocracy smothered, and that exploded once he was removed.

What neither Bush's critics nor defenders could foresee was his administration's mind-boggling indifference to establishing security in post-Hussein Iraq. In the absence of a credible central authority, the fragmentation of Iraq is already an established fact. Once-secular Basra, the largest city in the Shiite south, is now controlled by clergy sympathetic to Iran, with posters of the Ayatollah Khomeini adorning the town. Recently the mayor of Baghdad was forcibly removed from office, not by official forces but by a Shiite militia. Iraqi governmental officials protect themselves from terrorists with guards from their own tribes. And if the efforts to build a national republic founder, it's a safe bet that the Iraqi army, in which America has invested so heavily, will devolve into very well-armed factional militias. Should that happen, as Henry Kissinger recently observed on this page, "the process of building security forces may become the prelude to a civil war."

And what exactly is the role of U.S. forces, whether or not there's a civil war, in an Iraq that has split into a Shiite Islamic south, a Kurdish north and a violent and chaotic largely Sunni center? What is our mission? Which side are we on?

Indeed, the Bush presidency is perilously close to one of the greatest, and surely the strangest, foreign and military policy failures in American history. We lost in Vietnam, to be sure, but Vietnam would have gone to the Communists whether or not we intervened. The dissolution of Iraq, however, should it proceed further, is the direct consequence of Bush's decision to intervene unilaterally and of the particular kind of occupation that he mandated. And that dissolution, we should recall, goes well beyond the political. Unemployment in Iraq exceeds 50 percent. Electrical power is on, in midsummer Baghdad, for four hours a day.

At great expense in resources and human life, we have substituted one living hell for another in Iraq. Things may yet turn out better than I fear they will. But right now there's a sickeningly good prospect that we will have set in motion a predictable chain of events culminating in the creation of both a sphere of terrorist activity and a sub-state allied with the mullahs of Iran.

Last week U.S. forces in Iraq discovered what looked to be a cache of chemical weapons, but determined that the arsenal had been assembled by the insurgent thugs who emerged after Hussein's fall. We have created the very dangers we intervened to prevent. Some policy. Some president.

meyersonh@washpost.com