The United States recently noticed something unusual in North Korea’s weapons program: Its missiles started to work. Why? We discuss a surprising discovery. Guest: William J. Broad, who has reported on missile defense for decades. For more information on today’s episode, visit nytimes.com/thedaily.

Subscribe today at nytimes.com/podcasts or on Apple Podcasts and Spotify. You can also subscribe via your favorite podcast app here https://www.nytimes.com/activate-access/audio?source=podcatcher. For more podcasts and narrated articles, download The New York Times app at nytimes.com/app.