H-Bombs, its the fission not fusion
In the current media reports on the North Korean nuclear test seems to be a complete lack of understanding of what a H-Bomb is, despite the knowledge being public available. While it has a fusion element, that is not what gives it its greater yield, that is still the fission component, but more effectively.
As mentioned in the article the biggest problem with an atomic bomb is the energy released when fission starts is so great it blows the bomb apart, which leads to a low yield and lots of radioactive contamination from the unused uranium or plutonium.
Where as a convention A-bomb uses high explosives to try to hold the fissile material together during detonation, a H-bomb uses the result of fusion triggered by a smaller fission bomb, to constrain a larger fission bomb so it holds together longer producing a higher yield and less unused fissile material. The actual mechanism is massively intense X-rays from the fusion reaction causes ablative pressure on a uranium jacket surrounding the secondary fission device..
A H-bomb is really a fission-fusion-fission bomb, with the vast majority of the energy released coming from the fission not fusion.