OK, then. I'll answer for you:
We went to war because Iraq had 'Weapons of Mass Destruction'. Turns out they did not. Turns out that lots of folks in the intelligence community didn't think they did. Turns out the Bush admin cherrypicked the data that supported their claims, while ignoring what didn't.
I think anyone who voted for the war shares the blame, though it's impossible to imagine a scenario where we would have gone in had the Bush admin not led the charge.
FWIW - Somehow the entire delegation from my little hayseed state was able to see that the 'intelligence' was absolute crap. That's cold comfort, though.