Until World War II scientific interest in human anthrax cases was relatively minor compared to the focus on animal disease. Bacillus anthracis was discovered in 1850 by the French parasitologist Casimir-Joseph Davaine, who examined the blood of infected sheep under the microscope. Subsequent work, especially by Robert Koch, the famous German biologist, and the legendary Louis Pasteur in France, proved beyond doubt that this bacterium caused anthrax. It was with anthrax, in fact, that the germ theory of disease was firmly established. In 1876, Koch employed his pure culture techniques to discover the life cycle of anthrax (from the bacterium, with its bamboo-like rods, to its hardy spore form and back to bacterium again). At the time, though, he was much less concerned with the victims of "ragpicker's disease" (the colloquial German term for anthrax) than with the hundreds of thousands of grazing animals his native country was losing each year to anthrax. These repeated epizootics, common also in France and other European countries, damaged the food, textile, and leather industries dependent on animal products. In 1881 Pasteur followed up his successful development of a vaccine against chicken cholera with one for animal anthrax. In May of that year, he was pressured into an early public demonstration of the vaccine at a farm in Pouilly-le-Fort, forty kilometers outside Paris. The risk paid off. On June 2, with twenty-five vaccinated sheep alive and twenty-five unvaccinated ones dead, Pasteur was proclaimed a hero in the press and by his scientific colleagues.
Since World War II, the potential of anthrax as a biological weapon has focused national and international attention on its lethality for humans. Anthrax spores, tough enough to withstand bomb detonation and small enough to aerosolize, have been a preferred agent for every nation that has sought to develop and produce biological weapons. But the primary attribute of biological weapons, including anthrax, is that they have been experimented with but almost never deployed. Some restraints are a matter of international norms. Born of a repugnance for chemical weapons used in World War I, the Geneva Protocol of 1925, for example, prohibits the use in war of both chemical and biological weapons. Although several nations, including the United States and the USSR, formally reserved the right to use such weapons in reprisal if first used against them — and thus implicitly maintained the right to develop and stockpile them — only very rarely do the norms against using biological or chemical weapons break down. In modern times, the only significant use of biological weapons, including anthrax and plague, was in the late 1930s and early 1940s, when the Japanese Imperial Army undertook covert experiments on humans (which included vivisection) and deployed biological weapons against Chinese troops and civilians in Manchuria. The details of this historical anomaly have only recently been revealed.