NFU doesn’t compromise deterrence – nuclear use is ineffective & only leads to escalation.

Third, although supporters of calculated ambiguity fervently believe it maximizes deterrence, the evidence for such a claim is hardly definitive. Nuclear weapons did not deter the 9/11 attacks; the rise of the Islamic State; Russian interventions in Georgia, Ukraine, or Syria; or North Korean nuclear and ballistic missile tests. Nor have Indian and Pakistani nuclear weapons deterred risky conventional crises between the two countries over Kashmir, most recently in February 2019. The calculated ambiguity argument gained some support from the perception that during the 1991 Gulf War a U.S. nuclear threat had helped deter Iraqi leader Saddam Hussein from using chemical weapons against U.S. and coalition forces or Israel.18 As Scott Sagan has persuasively argued, however, it is highly unlikely that a nuclear threat in fact deterred Saddam from using chemical weapons.19 Indeed, recent research suggests that the threat to use nuclear weapons first against non-nuclear states has little credible coercive power.20

Fourth, even in the very small number of scenarios where nuclear weapons might seem to be necessary — for example, knocking out North Korean mobile missiles or underground command centers — opening the Pandora’s box of nuclear use would likely lead to uncontrolled escalation. There is no scenario in which using nuclear weapons first can make a bad situation better. As James Doyle, a former staffer at Los Alamos National Laboratory, has argued, “It is folly to believe that the use of nuclear weapons could de-escalate a conflict.”21