An unarmed intercontinental ballistic missile launches during an operational test at Vandenberg Air Force Base, California, in 2017.

For more than 30 years, major nuclear powers have refrained from testing nuclear bombs. But that streak may soon be over as Russia and the U.S. conduct missile tests and threaten to resume explosions ...

Is the world back to testing nuclear weapons? Here are the facts

For more than 30 years, major nuclear powers have refrained from testing nuclear bombs. But that streak may soon be over as Russia and the U.S. conduct missile tests and threaten to resume explosions ...