In an otherwise divisive, partisan debate on the Iraq war, the 75-23 bipartisan Senate vote to divide Iraq into autonomous regions was astounding. People who disagree on everything else about Iraq, such as conservative Republican Kay Bailey Hutchison of Texas and liberal Democrat Barbara Boxer of California, voted in favor of the non-binding measure.

The Bush administration and the international community, made up of many states that have their own restive minority populations, have been reluctant to reconcile themselves to the pragmatic Senate admission that Iraq is unlikely to have a unified democratic government.

The difference is that the Bush administration and the international community don’t have to face angry U.S. voters next year and many senators do. The Senate is grasping for anything that could stabilize Iraq before the 2008 election and realizes that unified, democratic government is unnecessary—and even counterproductive—toward that end. The ugly fact is that an incomplete and unratified partition of Iraq already exists on the ground and cannot be undone. Ethnic cleansing has separated populations, and local militias are providing security and services.

Twentieth-century partitions, some violence-riddled, some more successful, offer guidance on how best to proceed.

One of the lessons learned from the violent partition of South Asia into India and Pakistan in 1947 and the partitioning of Ireland in 1921 is that incomplete partitions are a recipe for violence and that substantial minorities, which threaten the majority population, should not be left on the wrong side of the partition line.

When the British divided South Asia into India and Pakistan, the well-armed Sikhs dreaded Muslim rule and wanted their own independent state or at least to be incorporated into India; but 2 million of them would have been stranded in Pakistan. Also, the region of Kashmir, which was two-thirds Muslim, was not partitioned at all. As a result, a war between India and Pakistan in 1947 and 1948 allowed India to take most of the province and left a substantial concentration of Muslims in the Indian part of Kashmir, leading to a Muslim insurgency that continues to the present.

The long-term violence in Protestant-dominated Northern Ireland resulted from a substantial Catholic community being left in the north (34 percent of Northern Ireland’s population) after the island was partitioned. Had these predominantly Catholic areas been allowed to go with the southern Republic of Ireland, most of this tragic violence could have been avoided.

Thus, an incomplete and unratified partition on the ground in Iraq is a dangerous situation, exacerbated by U.S arming and training of all factions, now including the Sunnis, which could make the ongoing civil war even worse.

Another lesson to be learned from the partition of South Asia is that population movements need to be encouraged, rather than discouraged, carefully orchestrated and protected with security forces. Financial incentives could be given to spur their movement.

The lessons of the partition of Palestine in 1948 are that all parties must agree to the partition (the Arabs didn’t), the partition should not be imposed by an outside power (the United Nations), and that defensible borders must be created for the resulting governments. In Iraq, a nationwide conclave must be held to work out the details of the division and draw the lines. The threat of a rapid U.S. troop withdrawal could be used as a catalyst to get the Shia and the Kurds, who dominate the Iraqi government, propped up by U.S. forces, to give the Sunnis oil fields, thus speeding their current evolution toward supporting a decentralization of Iraq.