Agent Orange was the code name for a herbicide developed for the military, primarily for
use in tropical climates. These herbicides were first used in the United States in the
mid-1940s to control broadleaf weeds in cereal grain fields, pastures, and turf. They also were used
to remove unwanted plants from rangeland, forests, noncropland, and waterways.
But serious testing for military applications did not begin until the early 1960's.
The purpose of the product was to "deny an enemy cover and concealment in dense terrain by defoliating trees and shrubbery where the enmy could hide," which basicly means they wanted to kill the plants so the enemy would have no where to hide. The product "Agent Orange" (a code name for the orange band that was used to mark the drums it was stored in, was principally effective against broad-leaf foliage, such as the dense jungle-like terrain found in Southeast Asia.
The product was tested in Vietnam in the early 1960's, and brought into ever widening use
during the height of the war (1967-68), though it's use was diminished and eventually
discontinued in 1971.