Before December 5th, every controlled nuclear reaction that has ever occurred in this world produced a huge amount of energy from very little fuel by atomic fission, the destruction of an atom’s nucleus (uranium) to form smaller atoms.
Since 1909, scientists have known nuclear fusion was possible. Fusion reactions fuse (join) two or more atoms together to form an atom with slightly lighter mass (weight in gravity) than the combined mass of the atoms that were fused. The missing mass is also converted into energy. The power output of a fusion reaction is far greater than the amount of energy it would take to fuse the atoms. A sustained fusion reaction is a “perpetual motion machine.”
The first nuclear explosions were fission reactions. The fusion reaction of the hydrogen bomb exploded in November 1952 made the fission bombs first exploded in 1945 look like firecrackers.