Part of the United States (US) strategy against the Viet Cong and North Vietnamese was to deny them cover and food.
Knowing that the area of Vietnam that borders Laos and Cambodia was a key transport route used to move troops and supplies from North Vietnam to the south, the US planned to defoliate large areas of jungle to hamper these movements. Other areas marked for defoliation were the Mekong delta, a Viet Cong stronghold, and areas used by the Viet Cong for food growing.
The defoliant of choice was a mixture of two herbicides, 24-D and 245-T, with kerosene or diesel fuel and an extremely toxic substance, dioxin. The mixture was known as 'Agent Orange' because of the orange stripe on the 55-gallon drums in which it was transported to Vietnam.
The US military sprayed Agent Orange from helicopters or low-flying aircraft to kill jungle growth. The herbicide and defoliant exposed Viet Cong and North Vietnamese troops who previously sheltered under the jungle's thick canopy.
Spraying began as early as 1961 in a campaign coordinated by America's Central Intelligence Agency. By late 1964, when US involvement in the war was on the rise, the defoliation campaign also gathered momentum, peaking between 1965 and 1967.
Australian troops were involved in the use of herbicides and insecticides. Insecticides were widely sprayed in Phuoc Tuy province, particularly at Nui Dat. Even during the war, herbicide use attracted growing criticism in the US, with the first reports of birth defects in children born in areas subject to aerial spraying appearing in 1965.
Concerns about the use of chemical sprays and its effect on people emerged in Australia during the 1970s. Australian veterans began reporting high incidences of cancer, while abnormalities in their offspring were also blamed on Agent Orange. The debate in Australia about links between chemical sprays and veterans' ill health was played out in the media as growing numbers of veterans came forward claiming Agent Orange had affected their health or that of their children.
The Australian Government at first denied that Australian troops had been exposed to chemical defoliants, but later retracted that in the face of contrary evidence.
The Vietnam Veterans Association of Australia (VVAA) lobbied hard on behalf of its members, but the material on which it relied was sometimes anecdotal and lacking in the kind of rigour necessary to prove a case.
In 1982, the VVAA published a list of symptoms by which a veteran might recognise the effects of exposure to Agent Orange. The list was sufficiently broad that many people could point to at least one sign of illness. As a result, repatriation clinics reported a high incidence of veterans presenting with one or more of the identified symptoms not long after the list was published.
Further studies followed, some commissioned by the government, until, under pressure from the VVAA, a royal commission was established in 1983. The commission's nine-volume report, issued in 1985, admitted the existence of health problems, but found no link to the use of defoliants in Vietnam. It did, however, acknowledge that certain chemicals may cause cancer and that a connection to illness in veterans was unlikely but 'not fanciful'.
Still not satisfied, the VVAA continued to prosecute its case against Agent Orange. Further reports, including a major study published by the Department of Veterans' Affairs (DVA), suggested that veterans' health was indeed affected by their war service and that in certain types of cancer, links with exposure to dioxin and other chemicals used in Vietnam did exist.
The issue of Agent Orange is made more complex by the fact that many veterans use the term generically to describe many of the chemicals with which they may have come in contact in Vietnam. Few Australians actually came into contact with Agent Orange, but many were affected by exposure to herbicides and pesticides. In cases where exposure to chemicals in Vietnam has led to ill health, DVA provides medical support and compensation.
Work in the US suggested linkages between herbicide exposure and some cancers. In Australia, despite the findings of higher incidences of some cancers and other illnesses among veterans than among the general population, reports have found, in the case of former national service men at least, that these men tended to live longer than their peers. As young men they, and indeed other soldiers, were generally fitter and healthier than others; many, it seems, remain so today.