This is very good, and you should read the whole thing.  My favorite from the list:

1.  Underestimating the enemy. As in Vietnam, the superpower’s potent military has been astounded by the tenacity and competence of a nationalist rebellion attempting to throw a foreign occupier from its soil. For example, the U.S. military, a hierarchical organization, views the Sunni insurgency as disorganized and without a central command structure. Yet the insurgents are using this decentralized structure very effectively and are not threatened by any U.S. decapitation strike to severely wound the rebellion by killing its leaders.

2.  Deceiving the American public about how badly the war is going. President Bush continues to talk of victory, and his chief military officer, Gen. Peter Pace, argued that the United States was making “very, very good progress” just two days before the more credible U.S. ambassador to Iraq warned that a civil war was possible in Iraq. President Lyndon Johnson painted an excessively rosy picture of U.S. involvement in Vietnam until the massive communist Tet offensive against the south in 1968 created a “credibility gap” in the public mind. The U.S. and South Vietnamese militaries successfully beat back the offensive, but the war was lost politically because the U.S. government lost the confidence of its own citizens. The Bush administration has fallen into the same trap by trying to “spin” away bad news from Iraq. Polls ominously indicate that Bush’s trustworthiness in the eyes of the American public has plummeted more than 20 points since September of 2003 to 40 percent.

3.  The Bush administration, like the Johnson and Nixon administrations, blames the media’s negative coverage for plunging popular support of the war. Yet the nature of the press is that it would rather cover extraordinary negative events, such as fires and plane crashes, than more mundane positive developments. Vietnam demonstrated that normal media coverage of mistakes in war could undermine the war effort. The Bush administration should have expected such predictable media coverage.

And then this one:

10.  Most important of all, starting a war with another country for concocted reasons, which did not hold up under scrutiny. Lyndon Johnson used a questionable alleged attack by Vietnamese patrol boats on a U.S. destroyer to escalate U.S. involvement in a backwater country that was hardly strategic to the United States. Bush exaggerated the dangers from Iraqi weapons programs and implied an invented link between Saddam Hussein and the 9/11 attacks. In a republic, the lack of a compelling rationale for sending men to die in a distant war can be corrosive for the morale of the troops and public support back home.

"Those who do not remember the past are condemned to repeat it." – George Santayana