Clarke's Testimony on 9/11:

"In a memo to National Security Adviser Condoleezza Rice, Clarke asked Rice and other policy makers 'to imagine a day after hundreds of Americans lay dead at home and abroad after a terrorist attack' and ask themselves what else they could have done to avert it.

The memo was dated Sept. 4, 2001...

Asked about the differences between his testimony to the staff and his book, Clarke said:

"There's a very good reason for that. In the 15 hours of testimony, no one asked me what I thought about the president's invasion of Iraq. And the reason I am strident in my criticism of the president of the United States is because by invading Iraq ... the president of the United States has greatly undermined the war on terrorism.""