In this May 2, 2003, file photo, President George W. Bush declares the end of major combat in Iraq as he speaks aboard the aircraft carrier USS Abraham Lincoln off the California coast. George W. Bush knows that history will shape his legacy more than anything he can say. But that's not gonna stop a guy from trying. After two years of near silence, Bush is back. With his new memoir and a promotion tour, the president who in cockier times could not think of a single mistake he had made, lists many. (AP Photo/J. Scott Applewhite, File)

Question: What was George W. Bush's biggest mistake during his 2 terms of office?