Public support for the war in Iraq has followed the same course as it did for the wars in Korea and Vietnam: broad enthusiasm at the outset with erosion of support as casualties mount. The experience of those past wars suggests that there is nothing President Bush can do to reverse this deterioration -- or to stave off an "Iraq syndrome" that could inhibit U.S. foreign policy for decades to come.

The current war in Iraq will generate a ferocious blowback of its own, which -- as a recent classified CIA assessment predicts -- could be longer and more powerful than that from Afghanistan. Foreign volunteers fighting U.S. troops in Iraq today will find new targets around the world after the war ends.

During Richard Nixon's first term, when I served as secretary of defense, we withdrew most U.S. forces from Vietnam while building up the South's ability to defend itself. The result was a success -- until Congress snatched defeat from the jaws of victory by cutting off funding for our ally in 1975. Washington should follow a similar strategy now, but this time finish the job properly.

Because they lack a coherent strategy, U.S. forces in Iraq have failed to defeat the insurgency or improve security. Winning will require a new approach to counterinsurgency, one that focuses on providing security to Iraqis rather than hunting down insurgents. And it will take at least a decade.