George W. Rathjens, one of SSP's founders, passed away on Thursday, May 26, 2016. Prior to coming to MIT he had a distinguished career in government service including the Department of State and the Department of Defense. He is best known for his contributions to the theory and practice of nuclear arms control. As a trained scientist he was able to participate in policy discussions with a fundamental understanding of the weapons and technologies at issue. He was a major participant in the controversial debate in the late 1960s and early 1970s on the wisdom of deploying ballistic missile defenses. Among other achievements, he was the Secretary General of Pugwash (1998-2002), the international non-governmental organization dedicated to bringing 'scientific insight and reason to bear' on the risks posed by nuclear weapons. For many years he had been an active participant in that organization, which won the 1995 Nobel Peace Prize. He was also intensely interested in the principal international security problems of the 1990s—humanitarian intervention, sovereignty, and human rights, and under his leadership Pugwash took up these issues in a series of conferences. Professor Rathjens was held in deep affection by his graduate students and colleagues.