Pyle and another instructor arranged for a briefing. They were taken to a huge building that once had been used to assemble railroad engines. It had a large black arch and, in one brightly lit room, an interior cage made of mesh wire. Pyle walked into the cage, where an officer showed him books containing mug shots. He looked in the first volume and saw a familiar face. It was Ralph David Abernathy, Martin Luther King's assistant. Officers called the books the "black list." As Pyle recalled it, they were actually labeled: persons active in civil disturbances. On a bench near the books was a stack of computer punch cards, the kind used in the 1960s to program the cutting-edge machines of the day. Written on the cards in pencil were the names of people whose information the cards contained. The top card was about Arlo Tatum, a man Pyle knew as the head of the Central Committee for Conscientious Objectors in Philadelphia, a group of activists who advised soldiers and others about their rights. Outside the cage, Pyle saw more than a dozen teletype machines. The head of the CONUS intelligence section told him they were spitting out reports from some fifteen hundred Army operatives about demonstrations with twenty people or more. Pyle was starting to understand how naive he'd been. He began formulating a plan. He would be getting out of the Army soon. He could tell the world about what was going on. When he joined the Army he took an oath to defend the country against all enemies, here and abroad. In his mind now, that included the Army's intelligence operation. They turned in their security badges and left the building.
"So I turned to the briefer and said, 'This is really terrific stuff. You are doing a great job. Do you have anything I can show my students?'" The briefer gave him teletype printouts for the week of March 11-18, 1968. One of the reports on it told of undercover Army agents attending a meeting at a Unitarian church. Pyle thanked him and turned in his security badge for the building. "It was very clear to me that we had just witnessed the essential apparatus of a police state," Pyle said. "It wasn't that these people were trying to create a police state. They were very nice people. The kind that you would want as your friends and neighbors. But they were creating a reporting apparatus that was covering millions of Americans engaged in completely lawful activity."
Pyle left the Army as planned, and in January 1970 he wrote a long story about the Army's vast and growing spy operations. The article, which won a Polk Award in 1971 for The Washington Monthly, began: "For the past four years, the U.S. Army has been closely watching civilian political activity within the United States."