The work of improving nuclear security is not done, though leaders are no longer meeting at the summit level. The threats of nuclear theft and terrorism remain very real. States, nuclear operating organizations, and institutions and initiatives supporting nuclear security must strive for continuous improvement in nuclear security. The alternative is dangerous decline. Achieving genuinely effective implementation of existing recommendations and commitments in five key areas could dramatically strengthen nuclear security around the world.

This spring, the United States hosted the fourth and final Nuclear Security Summit in Washington, DC. Senior representatives of more than 50 nations convened to mark the end of an unprecedented international initiative over the last six years to strengthen security measures aimed at preventing nuclear terrorism. During that time, many states made significant progress, but more work is needed.

The 2016 nuclear security summit was a pivotal moment for the decades-long effort to secure nuclear material around the globe. More than 50 national leaders gathered in Washington for the last of four biennial meetings that have led to significant progress in strengthening measures to reduce the risk of nuclear theft.

In the months and weeks before the 2016 Nuclear Security Summit in Washington, D.C., Belfer experts promoted a series of ideas to strengthen measures to prevent terrorists from acquiring nuclear weapons or the essential ingre­dients to make them.

My colleague Matthew Bunn has argued that nuclear security provides a foundation for all three pillars of the NPT. I agree with him. An act of nuclear terrorism would likely put an end to the growth and spread of nuclear energy. Nonproliferation cannot be achieved as long as stocks of highly enriched uranium or plutonium remain vulnerable to theft. And states will not give up the arsenals they possess as long as they believe that agents of an enemy state could steal nuclear weapons or materials to acquire a nuclear capability overnight.

"Today and tomorrow, world leaders will gather for what will likely be the final international summit on security for nuclear weapons and the materials needed to make them—a key tool for preventing nuclear terrorism. The last time this group met, at the 2014 Nuclear Security Summit in the Hague, they declared that preventing terrorists from acquiring nuclear weapons or weapons-usable materials remained “one of the most important challenges in the years to come.” Yet, since then, nuclear security has improved only marginally, while the capabilities of some terrorist groups, particularly the Islamic State, have grown dramatically, suggesting that in the net, the risk of nuclear terrorism may be higher than it was two years ago..."

"World leaders face a stark choice at the final Nuclear Security Summit later this week: Will they commit to efforts that continue to improve security for nuclear weapons, fissile materials, and nuclear facilities, or will the 2016 summit be seen in retrospect as the point at which attention drifted elsewhere, and nuclear security stalled and began to decline? The answer will shape the chances that terrorist groups, including the Islamic State, could get their hands on the materials they need to build a crude nuclear bomb...."

In this new report, Preventing Nuclear Terrorism: Continuous Improvement or Dangerous Decline?, Matthew Bunn, Martin Malin, Nickolas Roth, and William Tobey provide a global reality check on nuclear security. They note that effective and sustainable nuclear security capable of addressing plausible threats is the single most effective chokepoint preventing terrorists from acquiring a nuclear weapon.

Just one week after “implementation day,” when Iran completed its nuclear commitments and the nuclear-related sanctions were lifted, Martin B. Malin, Executive Director of the Project to Manage the Atom at Harvard University’s Belfer Center, spoke about the current state of non-proliferation affairs in the Middle East with Michael Moran, Visiting Media Fellow on Peace and Security at Carnegie Corporation of New York.

The Iran nuclear deal was officially implemented on Saturday, as Iran successfully fulfilled its initial key nuclear commitments and the international community relieved major sanctions, including unfreezing about $100 billion of Iranian money. Implementation Day was met with applause from deal supporters in the U.S. and Iran, while critics have raised questions about whether Iran will adhere to its requirements and how it will flex its newfound economic power. Also in recent days, the U.S. and Iran agreed to a prisoner swap that led to the freedom of Washington Post reporter Jason Rezaian and others, and negotiated the release of American sailors detained in Iran. What does the arrival of Implementation Day mean for Iran’s nuclear program and nuclear nonproliferation, and how does it bode for the future of U.S.-Iran relations? We asked Belfer Center experts to weigh in on these and related questions.