I've seen this referred to but not link over the last few days. I read it last night in the New Yorker. It's a must read.
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The point is not that the President and his senior aides were consciously lying. What was taking place was much more systematic—and potentially just as troublesome. Kenneth Pollack, a former National Security Council expert on Iraq, whose book “The Threatening Storm” generally supported the use of force to remove Saddam Hussein, told me that what the Bush people did was “dismantle the existing filtering process that for fifty years had been preventing the policymakers from getting bad information. They created stovepipes to get the information they wanted directly to the top leadership. Their position is that the professional bureaucracy is deliberately and maliciously keeping information from them.
“They always had information to back up their public claims, but it was often very bad information,” Pollack continued. “They were forcing the intelligence community to defend its good information and good analysis so aggressively that the intelligence analysts didn’t have the time or the energy to go after the bad information.”
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http://www.newyorker.com/fact/content/?031027fa_fact