So, why did they fight that war again?

US Vice-President Dick Cheney still seems to think that the invasion of Iraq was justified because Saddam was in bed with Osama. Unfortunately, the 9/11 Commission disagrees. Their preliminary statement on al-Qaeda says that

We have no credible evidence that Iraq and al-Qaeda co-operated on attacks against the United States.

While al-Qaeda had grovelled at Iraq back in the mid 90's to be allowed to set up training camps, Saddam told them to bugger off - and there was no collaboration post September 11th either.

So, why did the US fight that war again?