U.S. Should Embrace Using Nukes for Nuclear Threat Only, Experts Say If those countries develop their own arsenals "I believe we will cross over a nuclear tipping point, greatly increasing the danger of a nuclear catastrophe in the world," he said. "We must do everything in our power to prevent that from happening," Perry added. He and former Senator Sam Nunn and former Secretaries of State Henry Kissinger and George Shultz are sometimes called the "Four Horsemen of the Non-Apocalypse" for their key role in promoting revived discussion of nuclear disarmament. Evans said nuclear doctrine was a "lively issue" for debate among commission members because "there's still a constituency" for extended deterrence -- possible use of a nuclear-strategic...