Weapons
Thermonuclear Weapons
Fission weapons are actually not that efficient compared to the development of weapons of mass destruction after World War II. Thermonuclear weapons were built after the destruction of Hiroshima and Nagasaki. These more sophisticated weapons still use fission, but only as a heat source to induce nuclear fusion.
H-bombs (short for hydrogen bombs) are thermonuclear weapons that use both fission and fusion in stages. The energy released in one stage provides the required energy for the next stage to occur. It's like a tragic play in two acts: Act II can't occur before Act I. Make no mistake, it is a tragedy when these bombs go off.
Nuclear weapon testing was performed by the US in the Bikini islands of Hawaii and by Russia in the Arctic Circle. These geographic regions remain unsafe and have since remained deserted. Since radiation by-products, called radiation fall-out, can't be contained, there's no way to measure the extent of the damage that, at some level, generations of lifeforms are all exposed to.
Interestingly enough, the Nobel Committee awarded Andrei Skharov, one of the Russian nuclear physicists that helped designed the most dangerous thermonuclear weapon in history, the Tsar Bomba, the Nobel Peace prize in 1975.
The entire Cold War was about having weapons so terrible that no one would want to use them for fear of annihilation in retaliation. But that's for another section.