A police officer attends the opening ceremony of the Global Initiative to Combat Nuclear Terrorism conference in Miami, Florida, June 11, 2007.
Carlos Barria / Reuters

Nuclear deterrence makes the most sense at the most basic level: nuclear weapons deter use by an adversary for fear of retaliation in kind. Deterrence, therefore, requires survivable nuclear capabilities. From this fundamental requirement, there are now approximately 15,000 nuclear weapons in the world. Most of them are in the United States and Russia. The explanation for why there are so many lies in the layers of nuclear orthodoxy and doctrinal complexity that have accumulated like sediment atop the foundation of nuclear deterrence.

One gets to thousands of nuclear weapons by subscribing to requirements for extreme redundancy—not just a nuclear triad of bombers, submarines, and land-based missiles, but also air- and sea-launched cruise missiles to accompany them. Some missiles and all bombers carry more than one warhead. Massive targeting lists are needed to make sense of large numbers of warheads. Add to this the requirement to launch within minutes of

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