From nuclear attacks and accidental missile launches, to internet terrorism and nuclear smuggling, former U.S. Secretary of Defense Sam Nunn offers this interesting quiz about events that have or haven't happened in recent years.

Here are 14 alarming incidents that occurred in 1998 at Russia's nuclear facilities. They reveal failures in security and the impact of economic chaos on Russia's nuclear complex and the military personnel who man it.

Here's an outline of national security dangers that could potentially grow into 'A-list' scale threats to U.S. and international security. Four of the five dangers listed concern Russia and the safety and security of its arsenal of weapons of mass destruction. (Excerpted from Ashton Carter's and William Perry's forthcoming book, Preventive Defense.)