All through the twentieth century, scientists and doctors labored to find ways of fighting the germs that cause fatal diseases. Their goal was to stop the spread of disease. But a few scientists had a completely different and more sinister goal, namely to find ways of inflicting disease on their country's enemies. The idea is a simple one. Since disease germs can kill, they can be used as a weapon if they can be harnessed. This use of germs is known as germ warfare or biological warfare, the latter referring to the fact that germs are biological agents.

Biological warfare has never been used on a large scale. But germs have been used purposely to kill people, animals, and crops in numerous isolated incidents. Many of these events occurred in modern times, although earlier societies also used germs to kill...