In 1969, President Nixon announced the end of all American offensive biological weapons programs, and renounced the first use of chemical weapons. But it wasn’t until several months later that Nixon confirmed that the U.S. would end all military research into toxins, which can be created either in nature or in the lab.

Nixon chose to end that toxin research because of one man, our interviewee today. Dr. Matthew Meselson is well-known in biology for his Meselson-Stahl experiment, which demonstrated that DNA replicates semiconservatively, and has won myriad awards for his academic work. But his consulting work for federal agencies at several crucial moments in Cold War history may be Dr. Meselson’s greatest professional contribution.

Dr. Meselson is 94 years old. He graciously agreed to a conversation with Statecraft about one of those moments. The first part of our conversation is published below.

What You’ll Learn: How do you convince a president in one memo? How did Hungarian lunch ladies help lead to Nixon banning toxins for military use? Why did the Joint Chiefs of Staff want to develop anthrax? Why was Nixon reading Michael Crichton?