During World War II, there was a large push for recruitment of some of the best art students across the country to join the United States Army. They formed a “deception unit”, or a “ghost army” that appeared to look like a huge mass of soldiers, tanks, trucks and artillery. However, it was all smoke and mirrors, consisting of inflatable tanks, sound design, and clever applications of fake tank tracks overnight. Actors also met in pubs, planting false information. This distracted the enemy from the real troops who were gathering.
To learn more about this fascinating undertaking, which was only de-classified fairly recently, check out the podcast on the subject from 99% Invisible. (Photo from Retronaut/Mashable, England, c. 1939)