Danielle Brian, the executive director of the Project on Government Oversight, and Peter Stockton, the group’s principal investigator, have been warning for years about the mismanagement of American nuclear facilities. Their analysis of the problem and the documents that they’ve obtained were extremely useful.

I benefited enormously from reading the work of academics experts on nuclear terrorism and from discussing the subject with them. Matthew Bunn is a professor of practice at Harvard University’s John F. Kennedy School of Government and co-principal investigator of its Project on Managing the Atom. At Harvard, at the National Academy of Sciences, and in government, Bunn has played a leading role in the effort to ensure that nuclear weapons and fissile materials are never stolen. Scott D. Sagan, a professor of political science at Stanford University, has a unique grasp of both nuclear-security and nuclear-command-and-control issues. Siegfried S. Hecker, a former director of the Los Alamos National Laboratory and a professor in the department of management science and engineering at Stanford, spoke to me about some of the technical aspects of securing nuclear material and the importance of continuing to work closely with Russian nuclear scientists. William C. Potter, director of the James Martin Center for Nonproliferation Studies at the Monterey Institute of International Studies, is a leading expert on nuclear terrorism, non-proliferation, and the national-security policies of contemporary Russia. I am grateful for his help with those issues.

I learned much about the threat of Salafi-jihadist terrorism and weapons of mass destruction from Gary Ackerman, the director of the Unconventional Weapons and Technology Division, at the University of Maryland; Seth G. Jones, the director of the International Security and Defense Policy Center at the RAND Corporation; Anne Stenersen, a research fellow at the Norwegian Defense Research Establishment; and from the writings of Rolf Mowatt-Larssen, a senior fellow at Harvard University’s Belfer Center for Science and International Affairs. I’m not sure how they sleep at night.

For the past seven years, I’ve had two remarkable mentors in all things nuclear: Sidney Drell, a professor and deputy director emeritus of the SLAC National Accelerator Laboratory, Stanford University, and Bob Peurifoy, a former vice president and director of weapons development at the Sandia National Laboratories. Their views about nuclear terrorism helped to form mine. It’s hard to imagine public servants with a greater concern for the public interest. Any mistakes in these pages are entirely my own.