History of biological warfare

The modern concept of biological warfare involves the use of biological agents, of which there are pathogens, typically bacteria or viruses, and toxins, which are biologically produced poisons. The history of biological warfare begins in antiquity, but was transformed in the 20th century via industrial warfare and advances in microbiology such as genetic engineering.

In the ancient and medieval period, biological warfare commonly overlapped with chemical warfare. This included contamination of food, water, animals, weapons systems, fabrics. In the European Middle Ages, common weapons were poisoned arrows and catapults to launch cadavers or animal corpses. European colonization exposed native populations in the Americas and Australia to smallpox outbreaks, although evidence of successful intentional uses is limited.

In World War I, the German Empire targeted horses and livestock with anthrax and glanders while France used burkholderia. The use of biological weapons in international warfare was theoretically prohibited by the 1925 Geneva Protocol, but research continued, and Japan and the United States did not ratify it until the 1970s. During World War II many countries initiated large biological weapons programs as part of total war. The Empire of Japan became the first country to use enhanced pathogens. Its Unit 731 and other units, led by Shirō Ishii, dispersed pathogens throughout China during the Second Sino-Japanese War. Plague, cholera, typhoid, anthrax, glanders, and others were used, primarily from air-dropped bomblets filled with infected fleas, a form of entomological warfare. Research was furthered by forced human experimentation on civilians and prisoners of war. The United Kingdom, at Porton Down, and the United States developed advanced biological programs including anthrax bombs.

After the war, an American cover-up gave immunity to biological warfare leaders, from prosecution for Japanese war crimes, in exchange for information to further the United States biological weapons program. Scrutiny during the Vietnam War forced the United States to renounce biological weapons in 1969. This contributed to the 1972 Biological and Toxin Weapons Convention, which comprehensively prohibited their development, production, stockpiling, and use. However, due to its weak inspection measures stemming from the Cold War, an advanced Soviet biological weapons program flourished. Genetic engineering was used to enhance pathogens' climate and antimicrobial resistance. Stockpiled weapons were envisioned for intercontinental attacks against cities, battlefield employment, and anti-agriculture attacks. The 1979 Sverdlovsk anthrax leak, which killed at least 68 people, was the first indication to the world of a continued offensive program.

Ba'athist Iraq also developed a biological weapons program, weaponizing anthrax and toxins, before its disarmament post-Gulf War by the United Nations Special Commission. The unsolved 2001 anthrax attacks in the United States, a week after the September 11 attacks, heightened public fear of biological warfare as a weapon of mass destruction. False allegations by a US-led coalition that Iraq was maintaining its weapons of mass destruction programs played a major role in justifying the 2003 invasion of Iraq.