A-bomb far less powerful, according to experts
The announcement on Wednesday from the Democratic People's Republic of Korea that it had carried out a nuclear test brought to the front lines of global attention a phrase not often heard since the Cold War - "the H-bomb".
As opposed to the atomic bomb, the kind dropped on Japan in the closing days of World War II, the hydrogen bomb, or so-called "superbomb" can be far more powerful - experts said, by 1,000 times or more.
Pyongyang's first three nuclear tests, from 2006 to 2013, were A-bombs on roughly the same scale as the ones used on Hiroshima and Nagasaki, which together killed more than 200,000 people. Pyongyang announced on Wednesday that it had detonated its first H-bomb; while seismic data supported the claim of a large explosion, there was no immediate way to confirm the type.