While 9/11 was not the beginning of the Long War, it was the first time most Americans took it seriously. Historians can argue about its actual onset, was it the Marine barracks bombing in Beirut, or one of the many planes highjacked? Most managed to shrug off the bombing of the USS Cole, the Kobar Towers bombing, and the first abortive attempt to truck bomb the World Trade Towers.
By contrast, September 11, 2001, both was and was not a Pearl Harbor moment. When Americans tried to focus on an enemy they found that, unlike the 1941 attack, 9/11 didn't make clear where or whom to punish.
The jihadis who were attacking us hid among millions of Muslims who were just getting on with their lives. A fair few of the latter has a sneaking admiration for the attackers, but weren't angry or brave enough to join them. A draconian response by us could make them "angry or brave enough."
And so the Long War continues, with no realistic prospect of achieving victory, and no realistic alternative to continuing the fight. It is Samuel P. Huntington's "war of civilizations," happening in asymmetric fashion and thus in painfully slow motion.
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Later ... Mike Rowe of Dirty Jobs has a Facebook post you'll want to read. He reprints the exact transcript of 4 calls between a passenger on United flight 93 over Pennsylvania - one Tom Burnett - and Tom's wife Deena at home. Reading them choked me up.
It appears Tom Burnett was a ringleader in crashing the flight to save either the White House or the Capitol and the lives of hundreds of people at whichever was targeted. Rowe suggests Nike should have picked Burnett instead of Kaepernick for their ads. It's damn clear Burnett believed in something and sacrificed his life to achieve it.