There are countless recountings of the timeline that shows that Bush lied to the American people in his State of the Union Address in January 2003, and that Colin Powell did just about the same thing in his address to the UN Security Council a month or so later, and that Bush lied in his declaration to Congress before the actual invasion in March, 2003. Here's an example.
But nowhere have I seen reference to a hugely significant piece of evidence that the administration was going to invade Iraq regardless of the state of its possession of WMDs, and that's this: In the winter of 2002-03, the UN inspectors--Blix and al Barradei--were pleading with the US authorities to share with them any information in their possession about WMDs so that they, with unrestricted access to inspection (recall their white SUV's racing around Iraq in response to tips?) could track down WMDs--or not. But the US didn't, for months, lend a hand--not a whisper of information--and then finally, on the eve of Powell's UN speech, the US gave Blix a verbal report of WMD whereabouts ("unprecedented" that such a report wouldn't be in writing, said Blix), which the UN inspectors then chased down and found to be false. Not just once, but several times. "Garbage on garbage," was one UN inspector's evaluation of the US evidence.
I've never seen a single essay that calls these events to mind--the above-linked report makes a brief reference to US intransigence, but doesn't stress it--as telling as they are that the US had faulty information--and had learned it was faulty "on the ground." What more proof could there be that when Bush told the Congress, in his declaration before the invasion, that Iraq had WMD's, he lied, knowingly and intentionally?