John Jaech, UW mathematics alumnus (1951, BA; 1953, M.Sc.), passed away on January 3, 2025, at the age of 95. Internationally recognized for contributions to nuclear safeguards, John’s career spanned working for General Electric on the Hanford Nuclear Reservation and the Vallecitos Nuclear Center in California, leading the Mathematics Department at the Pacific Northwest National Lab, and then joining Jersey Nuclear (later Exxon Nuclear). He became the Chairman of the Institute of Nuclear Materials Management (INMM) in 1983-84, where he was also awarded the Distinguished Service Plaque and became a Fellow of the organization. He was a consultant to the International Atomic Energy Agency (IAEA) from 1972 to 2000 and a full-time expert sponsored by the US State Department at their headquarters in Vienna from 1985 to 1993, where he made important contributions on Statistical Methods to the IAEA Safeguards Technical Manual.