A weapon of mass destruction (WMD) is a biological, chemical, radiological, nuclear, or any other weapon that can kill or significantly harm many people or cause great damage to artificial structures (e.g., buildings), natural structures (e.g., mountains), or the biosphere. The scope and usage of the term has evolved and been disputed, often signifying more politically than technically. Originally coined in reference to aerial bombing with chemical explosives during World War II, it has later come to refer to large-scale weaponry of warfare-related technologies, such as biological, chemical, radiological, or nuclear warfare.
The histories of biological and chemical warfare date from antiquity to the modern period, with toxic gases used on a vast scale in World War I. In the 20th century, nuclear weapons were first developed, and were used in war twice, in the atomic bombings of Hiroshima and Nagasaki. Biotechnology allowed for the enhancement of pathogens as weapons, and advanced chemical weapons such as nerve agents were developed. Radiological weapons have never been used or mass-produced.
