PAUL H. JOHNSTONE (deceased) was a senior analyst in the Weapons Systems Evaluation Group (WSEG) in the Pentagon. He was assistant director of three crucial studies on outcomes of nuclear war and the director of a fourth, on the impact on civilians. He also initiated a series of “critical incident” studies recounting decision-making problems, which led to the McNamara study of the errors of Vietnam war policy known as The Pentagon Papers and was one of its authors.