North Korea jolted the rest of the world this week with its announcement that it had tested a hydrogen bomb. International leaders and observers aren't so sure it was a hydrogen device, but it has still caused great concern.
Former Georgia Democratic Sen. Sam Nunn has spent years studying the threat of nuclear expansion. He is the co-founder (with Ted Turner) of the Nuclear Threat Initiative and a distinguished professor in the Sam Nunn School of International Affairs at Georgia Tech.
During his years in the Senate, he chaired the Armed Services Committee. In a conversation with Denis O'Hayer on "Morning Edition," Nunn discussed the dangers North Korea's nuclear capability pose to its neighbors -- and some less obvious but equally troubling threats.