In the eight years of George W. Bush's presidency, the U.S. expended treasure and lives on futile searches for weapons of mass destruction, but was unwilling to take a lead in nuclear disarmament. As a result, the international consensus on nonproliferation was weakened, existing arms control regimes were damaged, and the disarmament process stalled.

Barack Obama vowed to change American foreign policy on disarmament, arms control and nonproliferation. He has changed the approach to handling nuclear proliferation crises, adjusted US nuclear weapons policy, and negotiated the new Strategic Arms Reduction Treaty (START). BY taking these initiatives he has restarted the nuclear disarmament process, is rebuilding the international consensus on nonproliferation and restoring US leadership on arms control issues.

A year ago in Prague, President Obama caught the world's attention with a speech on nuclear disarmament. Now he has returned to that city to sign the new START to replace the 1991 START that expired in 2009.

Nuclear disarmament by legally-binding treaty is in the interests of both the United States and Russia. The Cold War has been over for two decades and relations among the major powers have been transformed from military confrontation to economic interdependence. A global nuclear war is now unimaginable, making it both absurd and risky to retain nuclear arsenals numbering tens of thousands of warheads. In addition to the risk of accidental launch, there is the mammoth cost of maintaining these vast arsenals. Furthermore, nuclear weapons states are obligated under the Nuclear Non-Proliferation Treaty, to move towards nuclear disarmament. Existing nuclear powers, especially the United States, must lead by example if they expect to persuade other countries not to go nuclear.

The New START Treaty is the first step to a world free of nuclear weapons, but the treaty should not be oversold. It sets the ceiling for deployed nuclear warheads at 1550, for deployed ICBMs, SLBMs, and heavy bombers at 700 and for deployed and non-deployed launchers and heavy bombers at 800. The new treaty also includes simpler and less costly verification mechanisms than previous agreements. But overall the reduction in nuclear arsenals is comparatively moderate. After the cuts, the two countries remain by far the world's predominant nuclear powers.