It’s time for Plan B in Iraq. Stalemate is an ugly word, with all the associations it drags in from Vietnam. But we are now stalemated in Iraq, with the only exit being, well, exiting.

All the facts on Iraq are in, so conclusions can be reached.

What is beyond debate is that Iraq has slipped into a full replay of its inborn ethnic, religious, and tribal conflicts, which were long suppressed by the iron-fisted rule of Saddam Hussein. The country’s varied population is intent on driving the bloodbath to its ultimate parameters.

There is no need for the American armed forces to witness this slaughter of Iraqis by Iraqis, as their presence gives the barbarity the dignified pretext of a fight against the “American occupation.”

In fact, this is not a fight provoked by the Americans but one that was bound to happen in Iraq and is happening elsewhere in the Arab world — in Gaza and the West Bank, Algeria, Lebanon, and the Arabian Peninsula, among others — by populations, rulers, and tribal cultures unable to settle into the pluralistic comfort of being part of something.

Many of us who know this region well cautioned against this war before it commenced in 2002 and 2003 but then saw the merits of seeing it through.Today, we must again reach for the intellectually honest conclusion that we cannot attain any of the goals that would have made the enterprise worthwhile.

There will be no democracy in Iraq because it takes generations to instill such values. And there will be no regional stability, either, because Iraq’s turmoil feeds on a neighborhood in the Greater Middle East filled with the same contradictions, corruption of vision, and delusional thinking now driving the Iraqi civil war.

In that sense, Iraq is a more dire situation than Vietnam, where the communists at least had clarity of vision: They knew what they were after and saw the goalposts affixed firmly in the ground.

In Iraq, America has run into the vagaries of a bipolar Arab world that is deeply disoriented, bitter, angry, and so confused it knows not what to blame but pounces on the first savior to knock at its door. There, we now know, the goalposts will move constantly, so no end is in sight.

The Middle East affairs scholar Fouad Ajami sums up it well in his penetrating analysis of America’s Middle East voyage, “The Foreigner’s Gift.” The journey into the heart of the Middle East, he writes, “turned out to be a venture into the malignancies of Arab politics.”

Where America hoped to find gladness in deliverance from the mind-bending brutality of Saddam’s dictatorship, it met instead the scorching realities of “despotism, sectarianism, antimodernism, willful refusal to name things for what they are,” Mr. Ajami writes.

Like him, many of us who come from that region hoped, fervently, that its disease could be cured with American optimism in Iraq and the exceedingly energetic American spirit. However, we also know when the air has gone out of the tire.

The same illnesses in Iraq are endemic to the region.They are easily encountered among the Palestinian Arabs, Egyptians, Algerians, Saudis, and Iranians, people who are more anxious to delve into internecine account-settling than pursue liberation from ghosts of the past or something that resembles democracy.

What is going to happen, then, when America leaves, as it must? That is not the right question. Rather, the question at hand is what happens if it stays.

Any hope of salvaging the cornerstones of an eventual American solution will evaporate as American troops and their political masters become mired in hair-splitting with the neighboring meddlers: the Iranians, Saudis, Syrians, and others who are keeping Iraq’s sectarian war well supplied with energy. The American enterprise, regardless of its origins, stands for introducing a modicum of civility into societies with deep Bedouin traditions of domineering tribes raiding other tribes, with all the spoils going to the conqueror — that is, until the next round.

When these parties tire of slaughtering one another, as always happens in civil wars, that American ideal must continue to loom for them in the distance as their alternative hope.

But if America continues to baby-sit this sectarian war, it will not even have that much to offer, which is why enough is now enough.