FORTY-FOUR years before German Chancellor Angela Merkel discovered that the National Security Agency had been listening to her cellphone calls, President Nixon met with South Korean President Park Chung-Hee to discuss a substantial boost in American military aid to thwart a worrisome threat from North Korea.

That August 1969, summit meeting in San Francisco was as lopsided as a diplomatic mismatch could be: Well before the two men sat down, Nixon had a detailed list of what Park would ask for — and another list of what he was willing to settle for — all thanks to the cryptographers at the NSA, spying on yet another US ally. In that technologically primitive era, the agency easily intercepted scores of encrypted high-level South Korean government cables, handily broke the codes, and let the US intelligence community in on the most closely held secrets in the Seoul government.

That year, I was an Army Intelligence officer based in Hawaii, assigned to watch over North Korea, and one among many analysts who read those cables every day. For nearly two years, thanks to the NSA, my regular reading also included the intercepted and decoded secrets of other Asian governments that posed no obvious threat to the United States — Japan, Thailand, Indonesia, Malaysia, Singapore, Burma, the Philippines and, of course, South Vietnam. In the 1960s, NSA cryptographers were also flies on the wall inside the ostensibly secure foreign ministries of our allies across Europe, including the government of one of Merkel’s predecessors, Willy Brandt.