Question:

Did the tragedy of September 11th proceed from an intelligence failure or a risk assessment failure?

Answer:

An intelligence failure involves missing or misinterpreting a signal through a channel which an intelligence service should be monitoring. For example, the CIA's failure to detect and give warning about India's nuclear tests, which it had been assigned to monitor through espionage, communications and overhead reconnaissance channels, was a clear-cut failure of intelligence.

A risk assessment failure involves not appreciating the probability of an event happening, and consequently not allocating sufficient intelligence resources to monitor channels that might give warning.

The September 11th tragedy proceeded from a risk assessment failure. The US security establishment had underestimated the threat of a handful of hijackers converting an airliner a piloted missile. If they had properly appreciated this risk, they could have increased surveillance through channels likely to produce a signal. For example, counter-surveillance at airports, surveillance aboard planes through undercover federal marshals and crew members and dredging through the activities, including financial transactions and phone calls, of recently trained student pilots associated with Suicidist and extremist organization. To be sure, such surveillance prior to September 11th might have produced an intelligence failure (missed signals, such as the Algerian pilot in Minnesota). Or, possibly, an intelligence success. But because of the risk assessment deficiency, such intelligence coverage was not instituted. So it was a risk assessment failure.