Lesson #1: The United States lost. The first and most important lesson of Iraq war is that we didn't win in any meaningful sense of that term. The alleged purpose of the war was eliminating Saddam Hussein's weapons of mass destruction, but it turns out he didn't have any. Oops. Then the rationale shifted to creating a pro-American democracy, but Iraq today is at best a quasi-democracy and far from pro-American. The destruction of Iraq improved Iran's position in the Persian Gulf -- which is hardly something the United States intended -- and the costs of the war (easily exceeding $1 trillion dollars) are much larger than U.S. leaders anticipated or promised. The war was also a giant distraction, which diverted the Bush administration from other priorities (e.g., Afghanistan) and made the United States much less popular around the world.
This lesson is important because supporters of the war are already marketing a revisionist version. In this counternarrative, the 2007 flow was a huge success (it wasn't, because it failed to produce political reconciliation) and Iraq is now on the road to stable and prosperous democracy. And the costs weren't really that bad. Another variant of this myth is the idea that President George W. Bush and Gen. David Petraeus had "won" the war by 2008, but President Obama then lost it by getting out early. This view ignores the fact that the Bush administration negotiated the 2008 Status of Forces agreement that set the timetable for U.S. withdrawal, and Obama couldn't stay in Iraq once the Iraqi