dpa (TNS)

BANGKOK — The thermonuclear, or hydrogen bomb — of the kind that North Korea said it had tested Wednesday — was developed after the nuclear weapons used on Japan in World War II and is far more destructive.

The first hydrogen bomb, tested in November 1952 by the United States, yielded energy equivalent to 10 megatons of TNT — roughly 1,000 times larger than the atomic bomb dropped on Hiroshima seven years earlier.

In this new type of bomb, two types of hydrogen — deuterium and tritium — are fused into helium, thereby releasing energy.

A conventional nuclear weapon uses fission — splitting rather than fusing the nuclei of atoms — to create a less powerful explosion.

A hydrogen bomb uses an initial fission reaction to produce the high temperatures required for the more powerful fusion reaction.

Less than a year after the U.S. thermonuclear bomb test, the Soviet Union exploded their own H-bomb, starting a race to produce more “superbombs.”

The most powerful H-bomb ever detonated — and therefore the biggest ever man-made explosion — was used by the Soviets in 1961. Known as the Tsar Bomba, it produced a yield equivalent to 50 megatons of TNT.

©2016 Deutsche Presse-Agentur GmbH (Hamburg, Germany). Distributed by Tribune Content Agency, LLC.

Photo: Pyongyang citizens gather in front of a big screen at Pyongyang Railway Station in Pyongyang, capital of the Democratic People’s Republic of Korea, to watch a news report on the hydrogen bomb test on Jan. 6, 2016. North Korea announced Wednesday that it has successfully carried out its first hydrogen bomb test. (Lu Rui/Xinhau/Zuma Press/TNS)