Biological weapons may be employed in various ways to gain a strategic or tactical advantage over an adversary, either by threat or by actual deployment. Like some of the chemical weapons, biological weapons may also be useful as area denial weapons. These agents may be lethal or non-lethal, and may be targeted against a single individual, a group of people, or even an entire population. They may be developed, acquired, stockpiled or deployed by nation states or by non-national groups. In the latter case, or if a nation-state uses it clandestinely, it may also be considered bioterrorism.
There is an overlap between biological warfare and chemical warfare, as the use of toxins produced by living organisms is considered under the provisions of both the Biological Weapons Convention and the Chemical Weapons Convention. Toxins and Psychochemical weapons are often referred to as midspectrum agents. Unlike bioweapons, these midspectrum agents do not reproduce in their host and are typically characterized by shorter incubation periods.
Biological warfare has been practiced repeatedly throughout history. Before the 20th century, the use of biological agents took three major forms:
Deliberate poisoning of food and water with infectious material
Use of microorganisms, toxins or animals, living or dead, in a weapon system
Use of biologically inoculated fabrics
The earliest documented incident of the intention to use biological weapons is recorded in Hittite texts of 1500–1200 B.C, in which