The Threat of Biological Weapons in Modern Warfare

A weapon that you cannot see, hear, or smell. A weapon that can spread silently through a population for days before anyone realises an attack has happened. This is the unsettling reality of biological weapons, a category of arms that turns the building blocks of life itself into instruments of mass harm. Unlike a bomb or a bullet, a biological weapon works by exploiting nature’s own machinery, using disease-causing organisms or toxins to sicken and kill. As advances in biotechnology make once-rare scientific knowledge increasingly accessible, understanding these weapons and the global systems built to contain them has become essential to grasping modern security challenges.

What exactly is a biological weapon?
The agents
The delivery mechanisms
A long and troubling history
Outbreaks that revealed the danger
The growing threat from non-state actors
Why bioterrorism is so difficult to counter
The Biological Weapons Convention
The Convention’s weak spot
A networked approach to biosecurity
Why a network matters

What exactly is a biological weapon?

A biological weapon is designed to disseminate disease-causing organisms or toxins to harm or kill humans, animals, or plants. What makes them distinct from other weapons is their reliance on living agents or the poisons such agents produce. They can do far more than cause battlefield casualties. They can be used for assassinations, to infect livestock and crops to trigger food shortages, and to spread widespread illness, fear, and mistrust through a society.

Every biological weapon has two essential parts. The first is the weaponized agent itself, and the second is a delivery mechanism that gets the agent to its target. Neither part is dangerous as a weapon on its own. A deadly pathogen sitting in a sealed container harms no one, and an empty spray tank is harmless. It is only when the two are combined that a biological weapon exists.

The agents

Almost any disease-causing organism or toxin can, in principle, be turned into a weapon. These include bacteria, viruses, fungi, and the poisons produced by living things. The United States Centers for Disease Control and Prevention (CDC) classifies the most dangerous of these as Category A agents, which include anthrax, botulism, plague, smallpox, tularemia, and viral hemorrhagic fevers. These pose the greatest risk to public health and national security because they spread easily, cause high mortality, or both.

Crucially, these agents are often not used in their natural form. They can be enhanced to make them more suitable for mass production, storage, and dissemination. A pathogen might be modified to survive longer outside a host, resist treatment, or spread more efficiently, sharply increasing its destructive potential.

The delivery mechanisms

Past weapons programmes have built a wide range of delivery systems. These have included missiles, bombs, hand grenades, and rockets, as well as spray tanks fitted to aircraft, cars, trucks, and boats. Most lethal agents are intended to be released as aerosols, which cause infection when breathed in by the targeted population. The goal is to disperse the material widely so that it does not clump in a few locations, which is precisely why aerosols and hardy spores are favoured.

A long and troubling history

Biological warfare is not a modern invention. Humans have understood for centuries that disease can be turned against an enemy. One of the earliest recorded uses came in 1347, when Mongol forces reportedly catapulted plague-infested bodies over the walls of the besieged port of Caffa. Some historians believe fleeing ships then carried the plague to Italy, helping to ignite the Black Death that killed roughly a third of Europe’s population.

The pattern continued through later centuries. In the 1760s, British forces are recorded to have used smallpox against Native Americans. The twentieth century, however, brought industrial-scale programmes. During the Second World War, Japan’s notorious Unit 731 subjected prisoners to experimentation with cholera, smallpox, plague, anthrax, and other diseases. Japan also dropped plague-infected fleas on Chinese cities, and an estimated 580,000 Chinese died as a result of the Japanese bio-weapons programme.

Outbreaks that revealed the danger

Two episodes in particular show how these weapons cause limited but severe outbreaks. Between 1978 and 1980, anthrax was used during the civil war in Rhodesia (now Zimbabwe), producing almost eleven thousand human anthrax cases and 182 deaths. Then in 1979, a single accidental release exposed the world to the dangers of state programmes. At a Soviet military facility in Sverdlovsk, anthrax spores escaped into the air. More than sixty people died from inhalation anthrax, and a lengthy cover-up kept the truth hidden until Russian President Boris Yeltsin finally admitted Soviet involvement years later.

This history reveals an important truth. Biological weapons have rarely caused casualties on the scale of nuclear weapons, yet their potential remains terrifying. A 1993 study estimated that spraying 100 kilograms of dried anthrax spores over a major city could cause between one million and three million deaths. The gap between historical reality and theoretical potential is exactly what keeps security planners awake at night.

The growing threat from non-state actors

For most of history, the knowledge and resources needed to build a biological weapon were the preserve of well-funded state programmes. That barrier is eroding. Rapid advances in gene editing techniques, gene sequencing methods, and DNA synthesis tools are opening new possibilities in synthetic biology, and with them a new world of risks from both deliberate misuse and accidents.

The worry is that this technology is becoming cheaper, more widely distributed, and easier to use. As a result, an ever-growing range of actors could potentially misuse it. The danger no longer comes only from governments. It can come from terrorist groups, drawn by the relative accessibility, low cost, and high impact of biological weapons.

Why bioterrorism is so difficult to counter

Bioterrorism is the deliberate release of biological agents to cause illness, death, fear, or disruption. What sets it apart from conventional terrorism is that it exploits the invisible, contagious, and delayed effects of biological agents. Because symptoms can take hours or days to appear, an attacker can vanish long before anyone realises an attack has even occurred. Worse still, a deliberate attack can closely resemble a natural disease outbreak, making attribution extremely hard.

The 2001 “Amerithrax” attacks in the United States demonstrated the disruption a single actor can cause. Anthrax spores sent through the postal service resulted in five deaths, the preventive treatment of 30,000 people, and hundreds of millions of dollars in decontamination costs. Groups such as al-Qaeda and Aum Shinrikyo have also attempted to develop such weapons, though with limited success so far. The “dual-use” nature of modern biology, where the same research that develops vaccines could be turned to harm, sits at the heart of this challenge.

The Biological Weapons Convention

The international community’s main response to this threat is the Biological Weapons Convention (BWC), formally the Convention on the Prohibition of the Development, Production and Stockpiling of Bacteriological (Biological) and Toxin Weapons and on their Destruction. It opened for signature on 10 April 1972 and entered into force on 26 March 1975. Its historical significance is hard to overstate, as it was the first multilateral treaty to ban an entire category of weapons of mass destruction.

The Convention rests on a comprehensive prohibition. States Parties commit never to develop, produce, acquire, transfer, stockpile, or use biological and toxin weapons. It builds on the 1925 Geneva Protocol, which had only restricted the use of such weapons but did not ban their creation or possession. Today the BWC enjoys nearly universal membership, with around 188 states having joined. India signed and ratified the BWC in 1974 and remains a committed party, having since enacted domestic laws to prevent the misuse of biological materials.

The Convention’s weak spot

For all its symbolic and legal weight, the BWC has a serious structural flaw. Unlike the Chemical Weapons Convention, which is enforced through the Organisation for the Prohibition of Chemical Weapons, the BWC lacks an independent verification and inspection regime. There is no body that can inspect laboratories or formally monitor compliance.

Instead, the treaty relies heavily on confidence-building measures (CBMs), which are voluntary submissions in which states share information to build trust. Participation has historically been poor. In fact, 2022 was the first year that over half of all states parties submitted a CBM. Negotiations for a verification protocol were pursued in the late 1990s but ultimately collapsed, leaving this gap unfilled. At the Convention’s 50th anniversary meeting, India itself cautioned that bioterrorism had moved from a remote possibility to an imminent global risk and urged stronger verification systems.

A networked approach to biosecurity

Because no single treaty can address every threat, the global response has evolved into something broader: a coordinated, networked approach. This means weaving together many different organisations, agreements, and regimes rather than relying on the BWC alone. The aim is to enhance both global public health and security by monitoring and responding to biological threats, whether they are natural, accidental, or deliberate.

Several pieces fit into this network. The World Health Organization’s International Health Regulations (2005) help countries manage public health risks that may cross international borders. Export control arrangements like the Australia Group work to prevent the spread of materials and equipment that could be used to make biological weapons. National laws add another layer, with India having passed legislation such as the WMD Prohibition Act of 2005, which criminalises the illegal manufacture, transport, and financing of weapons of mass destruction and their delivery systems.

Why a network matters

The strength of this approach lies in its overlap. A natural pandemic, an accidental laboratory leak, and a deliberate bioterror attack can look remarkably similar in their early stages. A system built only for warfare would miss natural outbreaks, and one built only for public health would miss deliberate misuse. By connecting public health surveillance, disarmament treaties, export controls, and law enforcement, the network creates layered defences. Tools such as bio-forensics, which help trace the origin of an outbreak, and robust national implementation, including the oversight of dual-use research, are increasingly seen as essential multi-dimensional reinforcements to the BWC and global biosecurity.

This integrated thinking reflects a broader shift toward what experts describe as a whole-of-government and whole-of-society approach to biosecurity. The threat is too diffuse and too fast-moving for any one institution to handle alone. The same vigilance that catches a naturally emerging virus is the vigilance that would catch a deliberately engineered one, which is precisely why public health and security have become two sides of the same coin.

What do you think? Given that the Biological Weapons Convention still has no verification mechanism after fifty years, should the international community prioritise a binding inspection regime, or is the networked approach of overlapping institutions a more realistic safeguard? And as gene-editing tools become cheaper and more accessible, how should a country like India balance the immense benefits of biotechnology research against the risk that the same knowledge could be misused?

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Table of Contents

What exactly is a biological weapon? 🔗

The agents 🔗

The delivery mechanisms 🔗

A long and troubling history 🔗

Outbreaks that revealed the danger 🔗

The growing threat from non-state actors 🔗

Why bioterrorism is so difficult to counter 🔗

The Biological Weapons Convention 🔗

The Convention’s weak spot 🔗

A networked approach to biosecurity 🔗

Why a network matters 🔗