The New Strategic Arms Reduction Treaty (New START) between the United States and Russia officially entered into force in a low-key ceremony in Munich in early February–much to the delight of our military leadership, intelligence community, and just about every national security expert on the planet.

The national security case for the treaty is a no-brainer.

Signed by the United States and Russia in April 2009, New START caps each country’s deployed nuclear arsenal at 1,550 warheads. It restores an essential means of monitoring and verifying the size and location of these forces, which we haven’t had since the original START I treaty expired in December 2009.

By ratifying New START, the United States is sending a strong signal to the world that it can be a reliable partner and leader in promoting nuclear stability. The treaty will help buttress cooperative efforts with Russia and other states to secure and safeguard dangerous nuclear material, stockpiles, and warheads. It also enhances U.S. credibility as the administration seeks to strengthen international support for tougher measures against rogue states such as North Korea and Iran.

Despite New START’s substantive merits and overwhelming bipartisan support, the eight-month-long campaign to win the U.S. Senate’s approval was a knock-down-drag-out fight, the successful outcome of which was in doubt until the very end.

The treaty faced enormous obstacles in the Senate, the most significant being a political environment defined by extreme partisanship.

After the Senate approved the treaty by a 71-26 vote, Senate Foreign Relations Committee Chairman John Kerry noted that winning over 70 votes was a major accomplishment, given the Senate’s polarization. Ultimately, 13 Republicans voted for the treaty.

Rather than antagonizing their opponents, the Obama administration and its allies in the Senate kept New START on the path to approval by painstakingly working to build a bipartisan majority. Much to the chagrin of some treaty supporters, this required negotiation, compromise, and some concessions.

Equally important, the administration and its allies called on key military leaders and former Republican officials to stress the national security merits of the treaty and its importance for U.S. leadership.

In a political climate paralyzed by partisanship on other issues, the bipartisan vote of approval for New START demonstrates that it’s possible for Senators to put aside political differences in the name of the national interest. This bodes well for the Senate’s successful consideration of future national security issues, including the crisis in Egypt.

Nuclear weapons may have protected us during the Cold War, but today we live in a different time and face new dangers. Massive nuclear arsenals are useless against contemporary threats like terrorism, and they don’t prevent the proliferation of nuclear weapons in other states. In the 21st century, reducing nuclear stockpiles, securing vulnerable nuclear materials, and banning nuclear testing will be the hallmarks of a more secure world.

New START is an important part of this effort, but it is only the beginning. The United States and Russia should take advantage of the momentum created by the approval of New START to push ahead on reductions in all types of nuclear warheads as soon as possible.

These next steps won’t be easy. Opponents will be tempted to play politics with national security, as they did with New START. But the alternative is a more dangerous world.

Kingston Reif is the Director of Nuclear Non Proliferation at the Center for Arms Control and Non Proliferation.

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