We can now expect an innovative surge in global production of chemical and bioweapons--which have effectively just become a cheaper way to attack the U.S. (and its allies). But there's no reason to expect a reversal in the spread of nukes. Obama's hope seems to be that if America disarms, other countries will feel safer, and out of this some communal effort will arise, fueled by gatherings such as next week's 47-nation nuclear summit in Washington, to scrap the bombs, end the wars and usher in a new era of peace.

[Mr. Kyl is a Republican senator from Arizona. Mr. Perle, a fellow at the American Enterprise Institute, was assistant secretary of defense in the Reagan administration.] There is a fashionable notion that if only we and the Russians reduced our nuclear forces, other nations would reduce their existing arsenals or abandon plans to acquire nuclear weapons altogether. This idea, an article of faith of the "soft power" approach to halting nuclear proliferation, assumes that the nuclear ambitions of Kim Jong Il or Mahmoud Ahmadinejad would be curtailed or abandoned in response to reductions in the American and Russian deterrent forces -- or that India, Pakistan or China would respond with reductions of their own. This is dangerous, wishful thinking. If we were to approach zero nuclear weapons today, others would almost certainly try even harder to catapult to superpower status by acquiring a bomb or two. A robust American nuclear force is an essential discouragement to nuclear proliferators; a weak or uncertain force just the opposite.