The destruction of Hiroshima and Nagasaki in 1945 marked an end and a beginning. The close of the Second World War ushered in a Cold War, with a precarious peace based on the threat of mutually assured destruction.

Today the world is at another turning point. The assumption that nuclear weapons are indispensable to keeping the peace is crumbling. Disarmament is back on the global agenda.

The Cold War's end, 20 years ago this autumn, was supposed to provide a peace dividend. Instead, we find ourselves still facing serious nuclear threats. Some stem from the persistence of more than 20,000 nuclear weapons and the contagious doctrine of nuclear deterrence. Others relate to nuclear tests — more than a dozen in the post-Cold War era, aggravated by the constant testing of long-range missiles. Still others arise from concerns that more countries or even terrorists might be seeking the bomb.

For decades, we believed that the terrible effects of nuclear weapons would be sufficient to prevent their use. The superpowers were likened to a pair of scorpions in a bottle, each knowing a first strike would be suicidal. Today's expanding nest of scorpions, however, means that no one is safe.

My multimedia "WMD-WeMustDisarm!" campaign, which will culminate on the International Day of Peace (Sept. 21), will reinforce disarmament calls by former statesmen and grassroots campaigns, such as Global Zero. In September, groups will gather in Mexico City for a U.N.-sponsored conference on disarmament and development.

Though the U.N. has been working on disarmament since 1946, two treaties negotiated under U.N. auspices are now commanding the world's attention: the Comprehensive Nuclear-Test-Ban Treaty and the Nuclear Non-Proliferation Treaty.

My own five-point plan begins with a call for the NPT parties to pursue negotiations in good faith — as required by the treaty — on nuclear disarmament, either through a new convention or through a series of mutually reinforcing instruments backed by credible verification. Disarmament must be reliably verified.

Second, I urged the Security Council to consider other ways to strengthen security in the disarmament process, and to ensure non-nuclear-weapon states against nuclear weapons threats. I proposed to the Council that it convene a summit on nuclear disarmament, and I urged non-NPT states to freeze their own weapon capabilities and make their own disarmament commitments. Disarmament must enhance security.

My third proposal relates to the rule of law. Universal membership in multilateral treaties is key, as are regional nuclear-weapon-free zones and a new treaty on fissile materials. President Obama's support for U.S. ratification of the CTBT is welcome — the treaty only needs a few more ratifications to go into force. Disarmament must be rooted in legal obligations.

My fourth point addresses accountability and transparency. Countries with nuclear weapons should publish more information about what they are doing to fulfill their disarmament commitments. We still do not know how many nuclear weapons exist worldwide. Disarmament must be visible to the public.

Finally, I am urging progress in eliminating other weapons of mass destruction and limiting missiles, space weapons and conventional arms — all of this is needed for a nuclear-weapon-free world.

This, then, is my plan to do away with the bomb. Global security challenges are serious enough without the risks from nuclear weapons or their acquisition by additional states or non-state actors.

Disarmament will restore hope for a more peaceful, secure and prosperous future. It deserves everyone's support.