Chemical/biological warfare is the term used to describe the use of chemical or biological agents as weapons to injure or kill humans, livestock, or plants. Chemical weapons are devices that use chemicals to inflict death or injury; biological weapons use pathogens or organisms that cause disease. Pathogens include bacteria, viruses, fungi, and toxins (poisons produced by animals or plants).
The modern use of chemical weapons began with World War I, when both sides to the conflict used poisonous gas to inflict agonizing suffering and to cause significant battlefield casualties. Such weapons basically consisted of well known commercial chemicals put into standard munitions such as grenades and artillery shells. Chlorine, phosgene (a choking agent) and mustard gas (which inflicts painful burns on the skin) were among the chemicals used. The results were indiscriminate and often devastating. Nearly 100,000 deaths resulted. Since World War I, chemical weapons have caused more than one million casualties globally.