Prerequisites:

Description:

    This is what most people think of when one says "nuclear weapons".  This is the technology of putting just the right radioactive materials together in just the right way that a chain reaction occurs which releases really phenomenal amounts of energy, compared to all previous chemical explosives.
    If too many fission explosives are used within a habitable planet's ecosystem, the radioactivity level of the planet will go up, and thus the habitability will go down (except for exotic biosystems which are insensitive to radiation).