Vipin Narang is the Frank Stanton Professor of Nuclear Security and Political Science at the Massachusetts Institute of Technology. He is the author of Nuclear Strategy in the Modern Era and Seeking the Bomb. Follow him on Twitter @narangvipin.

Scott D. Sagan is the Caroline S. G. Munro Professor of Political Science, the Mimi and Peter Haas University Fellow in Undergraduate Education, and Senior Fellow and Codirector at the Center for International Security and Cooperation (CISAC) at Stanford University. He is the author of The Limits of Safety and coauthor of The Spread of Nuclear Weapons.