Preventing an era of nuclear anarchy: Nuclear proliferation and American security

(U.S. Air Force photo by Airman 1st Class Braydon Williams)

By Mariano-Florentino (Tino) Cuéllar, Ernest J. Moniz and Meghan L. O’Sullivan • Sep 29, 2025

Following decades of mostly successful efforts to combat the spread of nuclear weapons, multiple global trends are reviving the possibility of a world with more nuclear-armed states. These developments raise fundamental questions about whether the United States can and should prioritize efforts to stymie further acquisition of nuclear weapons in the twenty-first century.

Iran’s nuclear program is top of mind for many people as we write this foreword. In June 2025, Israel and the United States acted on long-standing threats to use military force to prevent Iran from crossing the nuclear weapons threshold. Yet as policymakers grapple with questions about Iran’s ability and desire to reconstitute a damaged nuclear program, major shifts across multiple domains are reshaping the broader nuclear threat landscape, with serious implications for U.S. strategy and security. Relations among the major nuclear powers are becoming more hostile. An increasingly assertive China is expanding its nuclear arsenal. Russia has backstopped its war in Ukraine with nuclear threats, and the last U.S.-Russia strategic arms control agreement is about to expire. Meanwhile, North Korea’s nuclear arsenal is still growing, and its threats to preemptively use nuclear weapons are unabated. These developments are adding strain to an already stressed Nuclear Non-Proliferation Treaty, which has served as the foundation of international governance of nuclear technology. At the same time, Washington must contend with the accelerating pace of technological development, alliance partners facing mounting regional security threats and uncertainty in the United States’ security commitments, and resurgent global interest in nuclear energy.

In short, the risks of more states acquiring, or at least pursuing, nuclear weapons are rising. The tools to manage these risks are weakening. And the long-standing consensus on where proliferation fits into U.S. national security strategy appears to be fraying.