WMDs

A weapon of mass destruction (WMD) is a nuclear, radiological, chemical, biological or other weapon that can kill and bring significant harm to a large number of humans or cause great damage to human-made 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, since World War II, it has come to refer to large-scale weaponry of other technologies, such as chemical, biological, radiological, or nuclear.

The first use of the term "weapon of mass destruction" on record is by Cosmo Gordon Lang, Archbishop of Canterbury, in 1937 in reference to the aerial bombardment of Guernica, Spain:

Who can think at this present time without a sickening of the heart of the appalling slaughter, the suffering, the manifold misery brought by war to Spain and to China? Who can think without horror of what another widespread war would mean, waged as it would be with all the new weapons of mass destruction?

At the time, nuclear weapons had not been developed. Japan conducted research on biological weapons (see Unit 731), and chemical weapons had seen wide battlefield use in World War I. They were outlawed by the Geneva Protocol of 1925. Italy used mustard agent against civilians and soldiers in Ethiopia in 1935–36.

...
Wikipedia