Earlier quoted context omitted.
So did the NSA know what the attackers were going to do? I find it very hard to imagine that the NSA and/or CIA would have let the attacks happen, even to protect key assets and methods. Maybe they had compromised some Mossad communication channel. Or maybe they had a double agent. But what would have been worth the risk to DC and NYC?
I agree that it is extremely unlikely they let it happen. I think if all the documents are ever declassified it will be a case study in the breakdown of communications in a large organization. There was office politics (FBI vs. NSA vs. CIA), no overall coordination, and plain incompetence to name a few things that were wrong. We see this all the time in large companies now, the difference is that rarely do people die…
I have always been curious about this as an organizational phenomenon. What percentage of documents are classified for actual security reasons as opposed to things like embarrassing the country or allies, covering up misconduct or outright illegal conduct, or just as the default reaction. Study would be impossible/impractical even with access, but it sure would be interesting.