TLDR: Biological warfare, also known as germ warfare, is the use of biological toxins or infectious agents like bacteria, viruses, insects, and fungi to harm or kill humans, animals, or plants during war. It is different from other types of weapons of mass destruction like nuclear or chemical weapons. Offensive biological warfare is prohibited under international law, but defensive biological research is allowed. Biological weapons can be used in various ways to gain an advantage over the enemy, but they can also have unintended consequences and be considered bioterrorism.
Biological warfare has been practiced since ancient times, with early examples including the use of poisoned arrows and infected cadavers. During World War I, there were reports of deliberate use of biological agents like anthrax and glanders, but the results were not very effective. In World War II, several countries, including the United Kingdom, the United States, and Japan, developed and tested biological weapons. The Japanese program, known as Unit 731, was particularly brutal and conducted human experiments on prisoners. After World War II, the use of biological weapons was prohibited by international treaties.
In the Cold War era, both the UK and the US had biological warfare programs, but they were eventually cancelled. Today, the use of biological weapons is considered a war crime, but there are concerns about the potential for bioterrorism and accidental release of biological agents.
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