As numbers-based arms control wanes, norms become even more important. Norms can be clarified in Codes of Conduct or established by customary practice. The most important norm in our field is the non-use of nuclear weapons in combat.

Few expected this norm to exist after atomic bombs were dropped on Hiroshima and Nagasaki – let alone to last for 70 years. As Nina Tannenwald has written in The Nuclear Taboo: The United States and the Non-Use of Nuclear Weapons Since 1945 (2007) “It is rare for a weapon found to be useful on one occasion to remain unused in the next.” And yet, this was the case during the Cuban Missile Crisis, as well as during the Korean, Vietnam, and Kargil wars. So far, the Bomb’s vast destructive powers have been confined by popular demand, wise decision-making, and divine intervention. Some would argue that deterrence also deserves credit for non-use, even though it has failed often enough. There’s some truth to this assertion, but nuclear weapons are more of a hindrance than a help in severe confrontations.

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