Nuclear weapons are devices that derive their destructive force from nuclear reactions, either fission or fusion. They release enormous amounts of energy in the form of an explosion and can cause devastating damage to people, property, and the environment. The term "nuclear" refers to the process of splitting atoms (fission) or combining them (fusion), which releases a massive amount of energy that can be harnessed for both peaceful and destructive purposes. Nuclear weapons have the potential to cause widespread destruction, as seen in the aftermath of Hiroshima and Nagasaki during World War II when atomic bombs were dropped by the United States. The use of nuclear weapons is considered a serious threat to global security and has led to efforts towards disarmament and non-proliferation.