Modern day herbicidal warfare resulted from
military research discoveries of
plant growth regulators during
World War II, and is therefore a technological advance on the
scorched earth practices by armies throughout history to deprive the enemy of food and cover. Work on military
herbicides began in England in 1940, and by 1944, the United States joined in the effort. Even though herbicides are chemicals, due to their mechanism of action (growth regulators), they are often considered a means of
biological warfare. Over 1,000 substances were investigated by the war's end for
phytotoxic properties, and the
Allies envisioned using herbicides to destroy
Axis crops. British planners did not believe herbicides were logistically feasible against
Nazi Germany. In May 1945,
United States Army Air Force commander
General Victor Betrandias advanced a proposal to his superior, General
Henry H. Arnold, to use of
ammonium thiocyanate to reduce Japanese
rice crops part of Allied
air raids on Japan. This was part of larger set of proposed measures to starve the Japanese in submission. The plan calculated that ammonium thiocyanate would not be seen as "
gas warfare" because the substance was not particularly dangerous to humans. On the other hand, the same plan envisaged that if the U.S. were to engage in "gas warfare" against Japan, then
mustard gas would be an even more effective rice crop killer. The
Joint Target Group rejected the plan as tactically unsound, but expressed no moral reservations.
Malaya During the
Malayan Emergency,
British Commonwealth forces deployed
herbicides and
defoliants in the Malaysian countryside in order to deprive
Malayan National Liberation Army (MNLA) insurgents of cover, potential sources of food and to flush them out of the jungle. The herbicides and defoliants they used contained
Trioxone, an ingredient which also formed part of the chemical composition of the
Agent Orange herbicide used by the
U.S. military during the
Vietnam War. Deployment of herbicides and defoliants served the dual purpose of thinning jungle trails to prevent ambushes and destroying crop fields in regions where the MNLA was active to deprive them of potential sources of food. In the summer of 1952, 500 hectares were sprayed with 90,000 liters of Trioxone from
fire engines; British Commonwealth forces found it difficult to operate the machinery in jungle conditions while wearing full protective gear. Herbicides and defoliants were also sprayed from
Royal Air Force aircraft. Historical records of
DOW chemical show that "Super Agent Orange", also called DOW Herbicide M-3393, was Agent Orange that was mixed with
picloram. Super Orange was known to have been tested by representatives from
Fort Detrick and DOW chemical in Texas, Puerto Rico, and Hawaii and later in Malaysia in a cooperative project with the International Rubber Research Institute. Discussions in the
British government centered on avoiding the thorny issue of whether herbicidal warfare in Malaya was in violation of the spirit of the 1925
Geneva Protocol, which only prohibited chemical warfare among signatory states in international armed conflicts. The British were keen to avoid accusations like the
allegations of biological warfare in the Korean War leveled against the United States. The British government found that the simplest solution was to deny that a conflict was going on in Malaya. They declared the insurgency to be an internal security matter; thus, the use of herbicidal agents was a matter of police action, much like the use of
CS gas for riot control.
Vietnam War . The
United States used herbicides in
Southeast Asia during the
Vietnam War. Success with
Project AGILE field tests with herbicides in South Vietnam in 1961 and inspiration by the British use of herbicides and defoliants during the Malayan Emergency led to the formal herbicidal program
Operation Trail Dust (1961–1971).
Operation Ranch Hand, a
U.S. Air Force program to use
C-123K aircraft to spray herbicides over large areas, was one of many programs under Trail Dust. The aircrews charged with spraying the defoliant used a sardonic motto-"Only you can prevent forests"-a shortening of the
U.S. Forest Services famous warning to the general public "Only you can prevent forest fires". The United States and its allies officially claims that herbicidal and
incendiary agents like
napalm fall outside the definition of "chemical weapons" and that Britain set the precedent by using them during the Malayan Emergency. Ranch Hand started as a limited program of defoliation of border areas, security perimeters, and crop destruction. As the conflict continued, the anti-crop mission took on more prominence, and (along with other agents) defoliants became used to compel civilians to leave
Viet Cong-controlled territories for government-controlled areas. It was also used experimentally for large area forest burning operations that failed to produce the desired results. Defoliation was judged in 1963 as improving
visibility in jungles by 30–75% horizontally, and 40–80% vertically. Improvements in delivery systems by 1968 increased this to 50–70% horizontally, and 60–90% vertically. Ranch Hand pilots were the first to make an accurate 1:125,000 scale map of the
Ho Chi Minh trail south of
Tchepone,
Laos by defoliating swaths perpendicular to the trail every half mile or so. Use of herbicides in Vietnam caused a shortage of commercial pesticides in mid-1966 when the
Defense Department had to use powers under the
Defense Production Act of 1950 to secure supplies. The concentration of herbicides sprayed in Operation Ranch Hand was more than an order of magnitude greater than that in domestic use. Approximately 10% of the land surface of South Vietnam was sprayed—about 17,000 square kilometers. About 85% of the spraying was for defoliation and about 15% was for crop destruction.
War on drugs in South America and Afghanistan ==Types of herbicides==