Our first big mistake was....
....invading Iraq in the first place. It was a bad idea from the very beginning. It has not served our national interests. We had no business starting a war there.
But having done so, our second big mistake was for George Bush to declare our "mission accomplished" shortly having gotten there. Mr. Bush completely underestimated the scale of the task ahead. As he oversold Iraqi WMDs to the American public, so too did he undersell the pricetag for undertaking this foolhardy endeavor.
We will be paying the price for this incompetence for decades.