I won't pretend to be educated on Iraq, on which of our moves were mistakes, or on whether going in was the right thing to do. I have become convinced that we won the war we meant to win, and are currently befuddled with one that we hoped never to fight.
It's always a bad strategy to plan on your opponent not doing the one thing that would really mess you up. If you are doing that, it is a prime indicator that you think your opponent is stupid, but it's really you who's registering low on the brilliance meter.
Stephen F. Hayes has put together a readable collection of facts that we learned shortly after the invasion, and that we know now. He is a journalist, and was in support of the original invasion. I think he strikes a good balance.
The article appears in Imprimis, the national speech digest of Hillsdale College. I recommend the digest, and the college in glowing terms to anyone interested.
Saddam's Iraq and Islamic Terrorism: What We Now Know.