Fission bombs are also known as atomic bombs, nuclear bombs, atom bombs, or A-bombs. These weapons derive their power from the splitting of atomic nuclei, which releases a tremendous amount of energy in the form of an explosion. Another synonym for fission bomb is a nuclear warhead, which describes the weapon's ability to deliver a nuclear explosive payload during armed conflict. Though they have been used only twice in history in warfare, their devastating power has caused them to be a major focus of international relations and arms control efforts. As such, nations have dedicated extensive resources to developing and improving fission bombs rendering a wealth of synonyms for the weapon.