Hilzoy nails it

Lessons learned from Iraq:

(1) It seems to me that our country went slightly crazy after 9/11, and one of the manifestations of that craziness was a tendency to say, about anyone who suggested stopping to think about much of anything, that that person just hadn't absorbed the lessons of 9/11, hadn't been there, hadn't fully grasped how horrific it was....

(2) Never substitute impugning someone's character for impugning his or her argument...

(3) One of the greatest strengths of our country is the fact that we allow debate and dissent. This means that if we choose to do so, we can debate policies before we adopt them, rather than first adopting them and only then, when it is too late, discovering the problems that a real debate might have made apparent...

(4) When the rest of the world thinks you're crazy, it's worth entertaining the possibility that they might be right...

(5) Beware of movements built on contempt... Sometimes, groups of people who spend years muttering about how different things would be if they were in charge are right. Often, however, they are not...

(6) Think very hard about the lessons of history...Trotting out Munich at every possible opportunity only ensures that the next time you find yourself in a Cuban Missile Crisis, your country will be turned to radioactive glass.

(7) Be very wary of extrapolating from the last few wars...

(8) Never underestimate the value of an exit strategy. By an exit strategy I do not mean the military plans for how, exactly, we might extricate our troops from Iraq, but a way of disengaging without seeming to have been beaten....[A]s Republicans are fond of reminding us, when we withdraw, al Qaeda and any number of other Islamists will take it as a victory, and will conclude that we can be outlasted. But that outcome is inevitable, unless we are willing to stay in Iraq forever, watching the men and women in our military die, along with more and more Iraqis.

(9) In wars, there are very few do-overs, and in occupations there are almost none....We need to get it right the first time. Eventually isn't good enough...

(10) Just because we're going to war doesn't mean we don't need diplomacy....

An excellent article, well worth reading.