This week's arrest of a Somali-born U.S. citizen as he attempted to detonate a car bomb during a Christmas tree lighting ceremony in Oregon was a chilling reminder that national security begins at home. It's one more reason why bringing our troops home from Afghanistan quickly needs to be more than "aspirational" (as the Pentagon recently termed the goal of being out by 2014). It's not just the at least $413 billion we'll spend between now and then trying to manage an unwinnable civil war (though it would certainly help with some much needed nation-building here at home). It's that every week -- from Yemen to North Korea to the Senate's likely refusal to ratify the new START treaty -- we are reminded of the many dangers to our national security emanating from all around the world, and including our own soil. The opportunity cost of remaining in Afghanistan is growing every day.
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