Biological warfare

Biological warfare refers to the deliberate use of pathogens, biological toxins or living organisms to cause harm, death or incapacitation in humans, animals or plants during conflict. These biological agents—ranging from bacteria and viruses to fungi and insects—are designed to exploit physiological vulnerabilities to achieve military or political objectives. Although historically widespread, the development and use of such weapons is now prohibited by international law, reflecting a strong global norm against their deployment.

Nature and Classification of Biological Agents

Biological weapons encompass a wide range of agents capable of producing disease or disruption. They may be lethal or non-lethal and can spread by direct exposure, contaminated materials or, in some cases, person-to-person transmission. Entomological warfare, involving the use of insects as vectors of disease, is regarded as a specialised subtype. Biological threats may be deployed overtly or covertly, and the use of pathogens for clandestine purposes is often categorised as bioterrorism.
Biological warfare is distinct from nuclear, chemical and radiological warfare, as well as from conventional kinetic weapons. Some toxins produced by living organisms occupy an intermediate position—known as mid-spectrum agents—because they are non-replicating yet biologically derived.

Legal Framework and Normative Prohibition

A strong international norm prohibits the offensive use of biological agents. Key milestones include:

• The 1925 Geneva Protocol, which forbids the use of biological and chemical weapons in armed conflict.
• The 1972 Biological Weapons Convention (BWC), which bans the development, acquisition, stockpiling, transfer and use of biological weapons. It allows research and biodefence activities solely for peaceful, protective or prophylactic purposes.

Violations of these norms in international armed conflict constitute war crimes under international humanitarian law.

Strategic Considerations

Biological agents possess a potentially high destructive capacity relative to their production cost and logistical requirements. They may offer strategic or tactical advantage through deterrence or disruption of enemy operations. However, several limitations constrain their military utility:

• Delayed onset of effects reduces immediate battlefield impact.
• Unpredictable spread, particularly for agents capable of airborne or person-to-person transmission, risks unintended harm to neutral or friendly populations.
• Difficulties in containment, including accidental laboratory release, pose serious risks.
• Environmental and meteorological dependency affects dispersal and effectiveness.

Despite these limitations, a credible biological threat can significantly alter diplomatic or strategic interactions between states or groups.

Accidental Exposure and Laboratory Risks

Historical cases demonstrate that laboratory research on dangerous pathogens can lead to accidental infection. Even trained personnel working under stringent safety procedures have occasionally contracted diseases such as Ebola, underscoring the inherent risks associated with handling high-consequence biological agents. Although such incidents do not indicate offensive intent, they highlight the potential for unintentional release.

Early History of Biological Warfare

Biological warfare has ancient origins. Early examples include:

• Hittite accounts (1500–1200 BC) describing infected individuals being sent into rival territories, possibly spreading diseases such as tularemia.
• Assyrian contamination of wells using toxic fungi.
• Use of poisoned arrows by Scythians and other cultures, often involving biological contaminants from cadavers.
• Siege of Caffa (1346), in which the bodies of plague victims were reportedly catapulted over city walls. Although historians debate its influence on the spread of the Black Death, it remains a notable instance of deliberate disease transmission during warfare.

In various African regions from the sixteenth century onward, mixtures of biological and toxic materials were used in combat, including the poisoning of opponents, water sources and livestock. Specialised practitioners were sometimes responsible for preparing such substances.

Eighteenth and Nineteenth Centuries

During the eighteenth century, allegations of intentional smallpox transmission occurred in several conflicts. Notable examples include:

• Siege of Fort Pitt (1763), during the French and Indian War, where smallpox-contaminated blankets were reportedly given to members of a Native American delegation. The extent to which this contributed to subsequent outbreaks remains debated due to pre-existing disease cycles in the region.
• American Revolutionary War, where rumours circulated that smallpox might have been deliberately used against Colonial forces, though contemporary leaders expressed scepticism.

Some historians argue that smallpox may have been intentionally introduced to Aboriginal populations in Australia in 1789, though this remains contested.
By the early twentieth century, advances in bacteriology enabled more systematic approaches. During World War I, attempts at biological sabotage involving agents such as anthrax and glanders occurred, though with limited success.

Developments in the Twentieth Century

Legal efforts to restrict biological warfare advanced with the 1925 Geneva Protocol, yet research programmes continued in several countries.
During World War II, the United Kingdom and other states developed biological research facilities. At Porton Down, studies explored agents including tularemia, brucellosis, anthrax and botulinum toxins. Testing on Gruinard Island demonstrated the devastating environmental persistence of anthrax spores, prompting long-term contamination of the site.
Parallel research activities occurred elsewhere, reflecting broader interest in biological weapons during the conflict. Subsequent ethical and humanitarian concerns accelerated international movements toward prohibition, culminating in the Biological Weapons Convention.