In just the first four months of the Trump administration, several pillars of American foreign policy have been upended — USAID dismantled, most foreign aid frozen, and the rules-based international trade system thrown into disarray. Could nuclear policy be next?

To find out, I spoke with Alexandra Bell, President and CEO of the Bulletin of the Atomic Scientists and a former senior State Department official on nuclear issues. She breaks down the key decisions facing the administration — and the risks tied to some of the options on the table, particularly around missile defense. We also unpack the state of nuclear diplomacy with Russia and China, and why forcing trilateral arms control talks is likely a dead end.

This conversation is a clear-eyed look at the current state of play in Trump’s nuclear policy — and where it may be headed next.

We recorded this live at the Carnegie International Nuclear Policy Conference. More conversations are coming soon. To catch them live, subscribe below or get the Substack app.

The Comprehensive Test Ban Treaty, better known as the CTBT, expressly prohibits its signatories from testing nuclear weapons. It was opened for signature in 1996 and is now one of the most widely adopted treaties in the world.

Since the Comprehensive Nuclear-Test-Ban Treaty was opened for signature in 1996, there have been ten nuclear tests conducted worldwide. These include two tests by India and two by Pakistan in 1998, and six tests by North Korea between 2006 and 2017 .​ This limited number of tests since 1996 stands in stark contrast to the more than 2,000 nuclear tests conducted in the preceding five decades, highlighting the CTBT's significant role in establishing a global norm against nuclear testing

My guest today, Robert Floyd, is the Executive Secretary of the Comprehensive Test-Ban Treaty Organization, which—as the name suggests—is the international body responsible for monitoring and facilitating the implementation of this treaty. It does so, in part, through a sophisticated global monitoring system capable of detecting a nuclear test anywhere in the world. I sat down with Robert Floyd on the sidelines of the Carnegie International Nuclear Policy Conference in Washington, DC, earlier this month, where he explained why the CTBT has been so successful in constraining nuclear testing—and what challenges the treaty now faces amid a rapidly shifting geopolitical landscape.

This episode is produced in partnership with Lex International Fund, a philanthropic fund dedicated to strengthening international law to solve global challenges. It is part of a series that demonstrates the impact of Treaties on state behavior that we are calling "when treaties work"

Ankit Panda’s new book delivers a stark message: we’ve entered a new nuclear age. This one is shaped by rising U.S.–Russia tensions, China’s emergence as a major nuclear power, and a wave of tech breakthroughs — including AI — that are transforming the nuclear landscape. The result? A world where nuclear security is more complicated, and more dangerous, than ever.

In The New Nuclear Age: At the Precipice of Armageddon, Panda breaks down the key trends driving this shift. In our conversation, he explains why this moment is so perilous — and how we might avoid stumbling into a new nuclear war.

We recorded this live at the Carnegie International Nuclear Policy Conference. More conversations are coming soon.