First, intelligence must be right. For this doctrine to work as a deterrent against rogue nations, our invasion of Iraq would have had to have produced verifiable WMDs and WMD programs. Our claims of Saddam's programs of WMD have turned out to be a conglomeration of poor intelligence, misleading evidence, and possibly out right lies. From Kim Il Sung's view, even if he does not have WMDs or programs to develop them, the survival of his regime is subject to inept intelligence reports and the whims of Washington policy makers who 'selectively' present evidence. And the susequent rational of 'Saddam was a bad guy,' while true, doesn't affect Pyongyang or Terran's view of the matter. From North Korea's standpoint, there is no incentive to actually remain WMD free. Regardless of actual actions, their survival is in peril.
Second, the pre-emptive doctrine becomes moot once one of these rouge nations is able to produce enough nuclear weapons to actually provide a deterrent of their own. If Pyongyang can develop enough nuclear weapons, the US is no longer able to attack North Korea pre-emptively. We, once again, enter an age of Mutual Assured Destruction (MAD) détente. The US is unable to invade a country that can hit the US with its nuclear arsenal.
Third, because US forces are tied up in Iraq, the US is not able to pose a substantial threat to Iran or North Korea for the foreseeable future. This, has in turn, given the two rogue nations a window of opportunity to develop nuclear weapons without fear of military intervention. Thus, this speeds up the incentive to develop WMDs while the US is unable to act. From the standpoint of Iran and North Korea, the window of opportunity is open as long as the US is tied up in Iraq. Once the US is able to disengage our forces from Iraq, we will once again become a threat to Iran and North Korea, so they had better develop their arsenals as quickly as possible before pre-emptive action is once again a viable action for the US.
Those who believe in the pre-emptive doctrine argue that it is negligent to wait for someone else to attack us before we attack them (reactive instead of pre-emptive). This is a very meritorious argument. Do we have to wait for Americans to die before we should act? This is not an easy question to answer, either morally or policy wise. Afghanistan was a reactive action after 9/11. Few can argue that our actions there were not merited. The question becomes, would our actions in Afghanistan have been a deterrent to others who may have wished to also inflict harm against us? My argument is that our actions in Afghanistan would have had more of a deterrent affect on the spread of WMDs than our pre-emptive actions in Iraq. We had shown the world that, regardless of direct or indirect involvement, a nation would be held responsible for their actions. If Kim Il Sung knows that if his direct or indirect actions lead to the deaths of Americans, that his regimes destruction is assured, he will be less likely to act then if he has got a 50/50 chance that we will invade regardless of his actions.
In my opinion, the pre-emptive doctrine has made us less safe that a reactive doctrine.
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P.S. this is also why Bolton is such a bad choice for the UN. He is already seen as someone who's own world view can lead to skewed fact presentation.
John R. Bolton has told the Senate Foreign Relations Committee that a policy maker should maintain the right to "state his own reading of the intelligence" even when it differs from that of intelligence agencies.
Senate Panel Is Set to Vote on Bolton Nomination Today