The C.I.A. sent a short but explosive message last week to all of its stations and bases around the world.The cable, which said dozens of sources had been arrested, killed or turned against the United States, highlights the struggle the agency is having as it works to recruit spies around the world. How did this deterioration occur?Guest: Julian E. Barnes, a national security reporter for The New York Times. Sign up here to get The Daily in your inbox each morning. And for an exclusive look at how the biggest stories on our show come together, subscribe to our newsletter. Background reading: Counterintelligence officials said in a top secret cable to all stations and bases around the world that too many of the people it recruits from other countries to spy for the U.S. are being lost.For more information on today’s episode, visit nytimes.com/thedaily. Transcripts of each episode will be made available by the next workday.