Given this background, it is not surprising that some have seen the US failure to avert the 9/11 attacks as creating an invaluable pretext for attacking Afghanistan in a war that had clearly already been well planned in advance. There is a possible precedent for this. The US national archives reveal that President Roosevelt used exactly this approach in relation to Pearl Harbor on December 7 1941. Some advance warning of the attacks was received, but the information never reached the US fleet. The ensuing national outrage persuaded a reluctant US public to join the second world war. Similarly the PNAC blueprint of September 2000 states that the process of transforming the US into "tomorrow's dominant force" is likely to be a long one in the absence of "some catastrophic and catalyzing event - like a new Pearl Harbor". The 9/11 attacks allowed the US to press the "go" button for a strategy in accordance with the PNAC agenda which it would otherwise have been politically impossible to implement.
The rest of the article is an interesting read, with lots of detailed references, and good links at the end. Joe Bob says "check it out".