Here's What The CIA Knew About 9/11 Before The Attack

It's hardly an exaggeration to say that the September 11, 2001, terrorist attacks were the most significant event — so far, at least — of the 21st century. The event, in which terrorists sponsored by extremist group al Qaeda flew hijacked commercial planes into New York City's World Trade Center and the Pentagon in Washington, D.C., has shaped nearly every aspect of the U.S.'s politics, culture, and foreign policy over the last two decades. In its immediate aftermath, though, there was only one question on a lot of Americans' minds: Could we have prevented this?

Like any other hypothetical question, this one is ultimately unanswerable, and those who have tried to answer it have undoubtedly been motivated to see things one way or the other. The intelligence community has every reason to portray themselves as having done everything they could have, while those in the White House obviously have just as much reason to portray themselves as having been inadequately informed — and of course, that's what you see in interviews. Still, when you look at the data, it's clear the FBI, the CIA, and others knew quite a bit. It's just unclear why no one managed to connect the dots — assuming they could have.

By 1998, U.S. intelligence had definite knowledge that Osama bin Laden intended to attack the U.S. in 2001, although they were short on details (via the U.S. Senate Select Committee on Intelligence). By 1999, Zacarius Moussaoui — later convicted of conspiracy for his involvement in the 9/11 attacks — had been placed on an FBI watch list.

In September 1999, the Library of Congress published a report warning of the possibility of a plane crash attack. In July 2001, the FBI circulated a memo warning that some trainees at U.S. flight schools could be al Qaeda operatives. By August 6, 2001, National Security Advisor Condoleezza Rice and President George W. Bush had both been briefed (via the Federation of American Scientists). On August 15, 2001, the Pan Am International Flight Academy alerted the FBI to their suspicions regarding Moussauoi, who had been training with them; eight days later, the CIA sent an urgent cable to the FBI warning them of a clear threat (via CNN). As of September 10, a plan to combat al Qaeda had hit the president's desk, but he had yet to sign it.

Hindsight being 20/20, it's easy to be frustrated by the White House's failures. As then-CIA counterterrorism chief Cofer Black (quoted in Politico) put it, "[H]ow is it that you could warn senior people so many times and nothing actually happened?" According to Rice, though, "I thought we were doing what needed to be done."

The History Channel will premiere the two-hour documentary "I Was There," marking the 20th anniversary of the 9/11 attacks, on Saturday, September 11. The trailer is posted on YouTube.