Fearing upcoming attacks, counterterrorism czar Richard Clarke wrote to National Security Advisor Sandy Berger on January 11, 2000, saying: “The CIA, the FBI, Justice and the NSC [National Security Council] staff had come to two main conclusions. First, the U.S. disruption efforts thus far had ‘not put too much of a dent’ in Bin Ladin’s network. If the United States wanted to ‘roll back’ the threat, disruption would have to proceed at ‘a markedly different tempo.’ Second, ‘sleeper cells’ and ‘a variety of terrorist groups’ had turned up at home.” Further, “The NSC staff had advised Berger that the United States had only been ‘nibbling at the edges’ of Bin Ladin’s network and that more terror attacks were a question not of ‘if’ but rather of ‘when’ and ‘where.’ ”

 – 9/11 Commission, The 9/11 Commission Report, Page 182