In the end, the military campaign was called Operation Ranch Hand, but it originally went by a more appropriately hellish appellation: Operation Hades. As part of this Vietnam War effort, from 1961 to 1971, the United States sprayed over 73 million liters of chemical agents on the country to strip away the vegetation that provided cover for Vietcong troops in “enemy territory.”

Using a variety of defoliants, the U.S. military also intentionally targeted cultivated land, destroying crops and disrupting rice production and distribution by the largely communist National Liberation Front, a party devoted to reunification of North and South Vietnam.

Some 45 million liters of the poisoned spray was Agent Orange, which contains the toxic compound dioxin. It has unleashed in Vietnam a slow-onset disaster whose devastating economic, health and ecological impacts that are still being felt today.

This is one of the greatest legacies of the country’s 20-year war, but is yet to be honestly confronted. Even Ken Burns and Lynn Novick seem to gloss over this contentious issue, both in their supposedly exhaustive “Vietnam War” documentary series and in subsequent interviews about the horrors of Vietnam.

More than 10 years of U.S. chemical warfare in Vietnam exposed an estimated 2.1 to 4.8 million Vietnamese people to Agent Orange. More than 40 years on, the impact on their health has been staggering.

This dispersion of Agent Orange over a vast area of central and south Vietnam poisoned the soil, river systems, lakes and rice paddies of Vietnam, enabling toxic chemicals to enter the food chain.

Vietnamese people weren’t the only ones poisoned by Agent Orange. U.S. soldiers, unaware of the dangers, sometimes showered in the empty 55-gallon drums, used them to store food and repurposed them as barbecue pits.

Unlike the effects of another chemical weapon used in Vietnam – namely napalm, which caused painful death by burns or asphyxiation – Agent Orange exposure did not affect its victims immediately.

In the first generation, the impacts were mostly visible in high rates of various forms of cancer among both U.S. soldiers and Vietnam residents.

But then the children were born. It is estimated that, in total, tens of thousands of people have suffered serious birth defects – spina bifida, cerebral palsy, physical and intellectual disabilities and missing or deformed limbs. Because the effects of the chemical are passed from one generation to the next, Agent Orange is now debilitating its third and fourth generation.