The Best Available Intelligence Can be Dead Wrong Or, Even Worse, Manipulated for Political Purposes - When the war was first launched, the prospect that evidence of Saddam's weapons program might never be found was a cringe-worthy nightmare scenario. It was impossible to imagine that Colin Powell's UN powerpoint was a work of fiction. We all know what happened next, and our trust in the intelligence establishment and the White House's use thereof has been irreparably shattered
When the World isn't Behind Us, That Doesn't Necessarily Mean They're Wrong - It's become an article of faith that the UN failed the test posed by Iraq four years ago. But how so? It doesn't take a UN-hugger to acknowledge that in refusing to ratify the war, the Security Council avoided the very same mistake Members of Congress are now admitting to one by one. One can argue that no matter what Saddam did, Russia, Moscow and even Paris would have given him a pass, but that wasn't put to the test.
The US Military Has Limits - Four years ago it was tough to imagine a scenario in which the mighty US military was, by all accounts, stretched to its limit. When we used to hear about the requirement of preparedness to fight two regional wars simultaneously, the prospect always seemed far-fetched. Some may be heartened that, the wisdom of such a potential option aside, launching a military confrontation right now with Iran is all but impossible. But we would rest easier if the military option were off the table only by choice, rather than by necessity as well.
Military Power Can't Accomplish Everything - Iraq has illustrated powerfully the limits of military power and the corresponding importance of diplomatic, economic, nationalistic and religious forces, as well as more abstract phenomena like international legitimacy. The problem we face now is fundamentally that our military presence has virtually no role to play in solving Iraq's political impasse. We have yet to work through the implications of this revelation for the conduct of US foreign policy, but doing so may change a lot about how the Defense and State Departments do business.
The Power of Our Ideals is Not Self-Evident - There's nothing wrong with having faith in American notions of freedom and democracy, but Iraq demonstrates that the triumph of these ideas in places geographically and culturally far-flung is anything but automatic. The Iraq experience further cautions that when clouded by the overlay of military intervention and occupation, the appeal of these concepts may become deeply obscured.
Going it Alone Isn't Always a Viable Option - One of the great things about superpowerdom is being able to take refuge in the idea that even if no one agrees with you, your resources make it possible to act alone and get things done. While that may often be the case, it isn't always. Had the Iraq occupation been truly multilateral from the start, the insurgency may not have built its terrifying momentum.
The Sophistication of a Military Confrontation Can be Dictated by the Lowest Common Denominator - For all our high-tech weaponry and sophisticated logistics and communications systems, we still find ourselves locked in a low-tech conflict where the weapons of choice are car bombs and IEDs. Our counter-insurgency tactics, likewise, are old-fashioned efforts to find and flush out terrorists, street by street and house by house.
Post-Conflict can be Tougher than Conflict, and Even More Important - Even before so-called nation-building was explicitly renounced by Condi Rice during the 2000 campaign, the US was ambivalent about its role in post-conflict stabilization missions. The result was that every time the US got involved, it had to reinvent the wheel, mustering resources and personnel anew. Hopefully the combination of Afghanistan and Iraq will be enough to convince skeptics that the US needs to take these operations, and related capabilities, seriously.
Cronyism has its Costs - There's something un-American about nepotism and no-bid contracts, but the incompetence, waste and cost overruns in Iraq illustrate that these practices have enormous tangible costs as well.
Not to Silence Dissent in the Name of Supporting the Troops - For the sake of American troops present and future, I hope we've learned this.