President Barack Obama's visit to Hiroshima came almost 71 years after the conclusion of a world war that was fought and ended with tremendous sacrifice, huge casualties and immense devastation. Today, global nuclear arsenals are capable of destroying not only cities but also civilization itself. Albert Einstein's prophesy bears repeating: "I do not know how the Third World War will be fought, but I can tell you what they will use in the Fourth - rocks!"
The United States and Russia deploy thousands of nuclear weapons ready to fire on a moment's notice, risking a catastrophic accident or miscalculation based on a false warning. Cold War dangers compelled dialogue between Washington and Moscow on nuclear security and strategic stability. This dialogue is dangerously absent now, even as our planes and ships have close encounters in Europe and the Middle East.
Globally, enough highly enriched uranium and plutonium to buildtens of thousands of nuclear bombs is spread across 24 countries, down from 36 in 2009.
Since 2007, former secretaries of state George P. Shultz and Henry Kissinger, former defense secretary William Perry and I have worked together on the steps needed to reduce reliance on nuclear weapons, keep them out of dangerous hands and ultimately end them as a threat to the world. That work must be put back at the top of the global agenda. We cannot predict whether or when the goal of a world free of nuclear weapons might be reached, but a clear U.S. nuclear policy goal consistent with the Nuclear Non-Proliferation Treaty is required to guide our diplomacy and defense.
Around the world, leaders must take practical steps to reduce nuclear risks now:
-- First, the agreement to curb Iran's nuclear program has significant regional and global implications for stopping the spread of nuclear weapons. All parties must live up to their commitments, assuring full implementation.
-- Second, North Korea's nuclear weapons and ballistic missiles threaten regional stability in Northeast Asia. We must work closely with our allies in South Korea and Japan to stop these programs and eliminate nuclear weapons from the Korean Peninsula. China must play a vital role in this joint venture.
-- Third, we should build on the progress to secure nuclear materials that Obama and other leaders have made at the fourNuclear Security Summits. Leaders must sustain the momentum of the summits and develop a global nuclear security system that covers all weapons-usable nuclear materials, including those held for military purposes. We must also make an all-out global effort to secure dangerous radiological materials and prevent a terrorist "dirty bomb."
-- Fourth, the United States and Russia cannot afford to treat dialogue as a bargaining chip when our two countries hold more than 90 percentof the world's nuclear weapons and weapons-usable nuclear materials. Most urgently, Washington and Moscow must rebuild a bridge of cooperation to ensure that neither the Islamic State nor any other violent extremist group acquires nuclear, radiological or other weapons of mass destruction.
-- Fifth, nuclear weapon states should avoid reckless rhetoric that can lead to disastrous mistakes. Split-second decisions made by those directly responsible for nuclear weapons and warning systems can be affected by the surrounding atmosphere. A poisoned political climate can lead to miscalculation, turning a false warning caused by a software glitch or a cyberattack into a nuclear exchange.
-- Sixth, in Washington, the question of "How much nuclear is enough?" must be asked and weighed against other urgent defense needs, with a focus on the need for stability among nuclear weapon states. Perry has called for a review of whether we should phase out our land-based missile force and for canceling plans to build a new air-launched nuclear cruise missile. Considering the growing terrorist threat, both the United States and Russia should reexamine the current practice of storing hundreds of short-range nuclear weapons in Europe. We must also bring the Comprehensive Nuclear Test Ban Treaty - a powerful nonproliferation tool - into force globally, including by securing U.S. Senate approval.
-- Finally, it defies human nature to build trust when weapons remain postured for mutual assured destruction. Washington and Moscow together must carefully dismount the "nuclear tiger" by reducing first-strike capabilities and fears, increasing warning and decision time for leaders and improving the survivability of their nuclear forces. We must escape the trap of continu
Obama's visit to Hiroshima should remind the world that we are in a race between cooperation and catastrophe. The day after a nuclear weapon explodes, God forbid, what would we wish we had done to prevent it? Why don't we do it now?
Sam Nunn, a Democratic U.S. senator from Georgia from 1972 to 1997 and co-chairman and chief executive of the Nuclear Threat Initiative, wrote this for the Washington Post.