Those are not necessarily mutually exclusive concepts. The prospect of an American counter-attack surely acts as a deterrent, to some extent, in the thought process of terrorists. Note that prior to the 9/11 attacks there was some dissension in the al Qaeda hierarchy over the wisdom of carrying out the attacks for fear of the American response. There were also those that viewed the U.S. as a "paper tiger" based on its timid responses to past attacks. That calculus may well have changed post-9/11 as a result of "revenge" carried out against al Qaeda and its enablers, thus providing protection to the United States from future attacks.

Of course, you give the GOP too much credit. The sentiment in terms of what the American response to 9/11 should be was nearly unanimous across the political spectrum. It just so happened that a Republican was President at the time and, therefore, served as Commander-in-Chief of the armed forces carrying out the response.

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