In terms of threat from nuclear arms outside of the U.S. and Russia, the long border shared by India and Pakistan might well be the most dangerous boundary on the planet. Theirs is a history troubled by sectarian violence, war and disputed territory. Both countries developed nuclear weapons in secret and both refuse to sign the Non-Proliferation Treaty.
"India and Pakistan probably have more than 100 nuclear weapons each, and they continue to build nuclear weapons," former Secretary of Defense William Perry said. "I've discussed this with leaders in both those nations; both believe they have good standards" for security and professionalism regarding the command and control of their weapons.
"We have no way of being really confident of that. And I am particularly concerned about Pakistan and not because the government does not want to maintain high standards, but because some important areas of the Pakistani countryside really are not under government control," including those close to nuclear-weapons storage sites. "I think there is a greater danger of weapons being lost or stolen under circumstances like that."
Perry is even more worried their owners will use those weapons. India and Pakistan have had three wars in a still unresolved territorial dispute over the region of Kashmir.
If a conflict were to break out again, "It would now be a war between two nuclear powers, and the danger of that war escalating into a nuclear war I think would be reasonably high."
And a nuclear exchange involving countries with large military forces such as these "is a catastrophe of a level most people's mind cannot fully encompass," he added.