Letting the treaty expire would increase the risk of nuclear conflict and open the door to an accelerated nuclear arms race. New START’s strictures on the number of deployed weapons did not prevent the U.S. or Russia from investing in a new generation of nuclear weapons. Its statement in support of that judgment urged the leaders of the major nuclear weapons states to shed their complacency and take action to rein in nuclear arsenals and reduce the risk that they will be used. Reversing current trends and restoring a commitment by the major nuclear powers to reduce and eventually eliminate their nuclear weapons arsenals will require more constructive relations among the U.S., Russia, and China. But even at the height of the Cold War major agreements to curb nuclear weapons development and deployment were reached, from the Limited Test Ban Treaty of 1963 to the Nuclear Nonproliferation Treaty of 1970.