On a combative opening day of the NATO summit in Brussels, President Trump called other member countries “delinquent” on military spending and attacked Germany as a “captive” of Russia. We examine where his frustration is coming from. Guest: David E. Sanger, a national security correspondent for The New York Times and the author of “The Perfect Weapon: War, Sabotage, and Fear in the Cyber Age.” 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.