The Vietnam War surfaced an important fact: The ability to see at night as effectively as during the day is indispensable. During the conflict, the Army fielded the first generation image-intensified tube systems. These systems added a new dimension to the tactics of land warfare. Taking the night away from the Vietcong was the goal during the late sixties and the early seventies, and it was attacked with ingenuity, enthusiasm, and a sub-stantial number of research and development contracts to U.S. industry.
Richard W. Sears,
"Evolution Of Forward Looking Infrared", Proc. SPIE 0313, Thermal Infrared Sensing Applied to Energy Conservation in Building Envelopes, (12 March 1982); doi: 10.1117/12.932895; https://doi.org/10.1117/12.932895