I've talked about the comparisons for a long time, and bits and pieces have come together, but I'd say this is the compilation of it all: how Iraq is far more like Vietnam than we think.
Details after the jump...
1. Airpower does NOT win the war: Airpower is great, don't get me wrong. But Rolling Thunder and "shock and awe" were ultimately disasters. They didn't help the problem. They did little to achieve the means of victory. Robert McNamara stated that the amount of airpower it took to even make a small dent in VC supplies through the Ho Chi Minh trail was huge. Rolling Thunder, while knocking out virtually all electrical power and manufacturing capabilities, didn't slow down the agrarian culture of North Vietnam. In Iraq, airpower did not kill Saddam Hussein, his kids, or any other top leaders. It killed Zarqawi only with the use of ground force in conjunction with airpower. It is only useful against standard ground armies, not against insurgencies.
As I pointed out in the comments below, if airpower and Predators hadn't been such a large part of the Rumsfeldian plan, ground troop levels would've been higher, thus raising our chances of success instead of reducing them.
2. This is a civil war, not a battle against ideology: In Vietnam, we confused nationalism with Communism, failing to recognize that Communism was just a means to a nationalistic end on the part of the NVA. The constant insurgency that we faced on the part of the VC was because they were fighting a civil war with the South, not because they were Communists that were part of the Moscow-Beijing sphere. They gladly took the aid from those nations, but did not follow their instructions all the time.
In Iraq, we're facing a mix that is 95% Sunni insurgents, 5% al-Qaida. We're equating the insurgency with terrorism, believing that their activities are being directed with al-Qaida, when in reality, if we were to leave, the insurgents would toss al-Qaida out because they have no stake in Iraq. And how can we say that our leaving would create an Islamic theocracy, when the current leaders in Iraq are far more disposed to theocracy, and the Sunnis are the ones who are secularists? We've completely misread the situation, because our government ignored any intelligence that did not fit their ideology. This is a civil war, not a terrorist battle. At this point, our staying only makes it worse. As much as I absolutely hate to say this, Saddam was the only plug on the sectarian differences, and by removing him, we created the climate for this. Had we put in enough force at the start, the civil war never starts and a coalition government could've gone into place easily.
3. Civilian leadership overriding military leadership in every aspect: One of the great failures of Vietnam is the failure of the Joint Chiefs to be more independent, to not let military competence be buried by political leadership. We escalated Vietnam without any thought as to the endgame and when we could leave, and we made military decisions based on political equations. It was all Cold War posturing, not wanting to look weak on Communism, the same way Iraq was wrongly tied in with terrorism. It's horrible.
Iraq is the exact repeat of this situation. Rumsfeld made Tommy Franks fit HIS equation, not the military one. Bush's timetable for Iraq was run on a political timetable, holding the vote before the midterms, and starting the war with enough time to possibly wrap it up for the 2004 general election season. All of the Iraq decisions have been based on making Bush a hero, not on what's right for Iraq, not on what's right for America, not on what's right militarily, but based on what makes the best propaganda for the President. It's a disgrace, and the Congress is at fault for allowing it to happen in the name of their political asses.
There might be more comparisons, but I believe these were the three strongest points out there, and we should repeat them over and over again until the election. I talked with a Vietnam vet recently, and he was pissed that our soldiers are being hung out to dry in Iraq. We need to get all the pissed-off people in this country feeling the same way, so they see that ending the rubber stamp is in their best interests, the soldiers' best interests, and the nation's best interests.
We didn't see the signs in Vietnam. In Iraq, we REFUSE to see the signs. In both cases, our defeat is both incompetence and hubris, the worst combination of them all.