From 1949 to 1969, the US government carried out at least 239 tests on unsuspecting US civilians that were meant to simulate biological weapon attacks.

Officials back then used what they believed were harmless "simulants" of actual bioweapons. But Leonard Cole, the author of the investigative book "Clouds of Secrecy: The Army's Germ Warfare Tests Over Populated Areas," tells Tech Insider that these supposedly harmless germs are "all considered pathogens now."

A newly declassified 1952 Department of Defense film, released on Sept. 30, 2015 in response to a FOIA request by the site Government Attic, shows the enthusiasm with which the DoD viewed those tests at the time.

Both in tone and content, it's hard to believe, especially from the non-Cold War perspective of today.

Government Attic posted a copy of the video on October 12, and Tech Insider verified its authenticity by comparing it to a version provided by an official at the US National Archives.

We've broken the film down into GIFs for easy viewing, with the full version at the end of the post.