For the past half century, the ultimate military deterrent for the US has depended on its stockpile of nuclear weapons. Because of technical, military, and political considerations, the decision was made nearly one decade ago, during the administration of President George Bush, that no new designs of nuclear weapons are needed and no nuclear‐explosion testing is required for the fore‐seeable future. (Such nuclear tests do not include experiments that are either nonexplosive—using a pulsed reactor, for example—or subcritical, involving no self‐sustaining nuclear reaction.)