In the 1950s, US military carried out secret tests of dispersal of agents simulating biological weapons in inhabited cities of the United States, without ever informing the local populations about what was happening. The experiments included the release of microorganisms that at the time were considered harmless.
The tests began in the context of the Cold War, which started shortly after World War II, when fears arose that spies from countries enemy to the USA could use biological weapons against American cities. The threat of an attack of this kind led military authorities to want to better understand the potential effects.
In 1949, a special operations division was created at Camp Detrick, specifically responsible for this work. This division aimed to test and evaluate the devastation that a potential biological weapons incident could cause on American soil.
The tests consisted of exposing specific areas to different types of bacteria and chemicals, in order to simulate the conditions of a real attack and to collect data on the spread of agents in the urban environment.
