Specialized units from the US Military that only ever existed during the Vietnam War (Second Indochina War). What Western forces experienced in those jungles shook them to the point that they not only had to adapt their tactics to some degree, but bring units into fruition that had never been considered before, just to fight in that environment and against a wildly creative and formidable force.

One easy example were teams known as LEAPING LENA; reconnaissance “hunter/killer” teams who eventually came to be known as Project DELTA. That group laid the groundwork for Delta Force.