When the white powder started falling from the sky, the soldiers were puzzled. Usually the American planes dropped bombs. Now, they were unleashing clouds of something that looked like fog, smelled like garlic and burned their eyes.
"The whole earth was covered with it," remembers Tong Van Vinh, who was a 26-year-old truck driver in the North Vietnamese military at the time. "We thought they were dropping smoke bombs on us. We didn't know it was a chemical."
A few weeks later, Mr. Vinh began to understand the terrible power of the strange clouds. "The trees died. Even the grass died. When we went to collect branches and leaves to disguise our trucks, there were none left."
This was Agent Orange doing its job. Keen to destroy the enemy's crops as well as the forest concealing its troop movements and supply lines, U.S. forces had resorted to the most powerful defoliants they could find, dropping about 80 million litres in all. But the chemical concoction killed more than plants; laced with dioxin, it was one of the more toxic substances known to humanity - so toxic, in fact, that the man who invented Agent Orange spent much of his life trying to keep it from being used.
"Nothing that you do in science is guaranteed to result in benefits for mankind," said U.S. biologist Arthur Galston, who died last month at the age of 88. "Any discovery ... can be turned either to constructive ends or destructive ends."
As the North Vietnamese soldiers were to discover, the "destructive ends" for Agent Orange were anything but fleeting; in fact, they have yet to subside. More than three decades after the fall of Saigon, the scourge known as the "last ghost" of the Vietnam War still haunts the children, and now the grandchildren, of its initial victims - an estimated three million people.
First sprayed in 1968, Mr. Vinh was plagued by muscular and skeletal disorders. But after the war ended in 1975, his health deteriorated rapidly. By 1994, he was paralyzed and spent six months in hospital, being fed liquids through his nose. He recovered, but not enough to work on his rice farm. Today, his voice is hoarse, he can't swallow solid food, his spine is numb and often he is too weak to walk or even to turn over in bed.
Dioxin interferes with reproduction, so Mr. Vinh's nightmare swept up his children and grandchildren as well. One son is blind and mentally handicapped. Another is deaf. A third has spinal problems. One daughter is partly paralyzed, another mentally handicapped, the third chronically weak with children born blind.
Vietnam estimates 400,000 people were killed or maimed by the defoliants, 500,000 children have been born with defects from retardation to spina bifida and a further two million people have suffered cancers or other illnesses. Yet they have received no compensation from those who produced the chemicals and those who made them a weapon of war.
Mr. Vinh survives on a $60 monthly pension - far from enough to cover his medical expenses, let alone those of his children. "We hope the U.S. will provide help for us," he says quietly.
So far, that seems unlikely. In February, a U.S. court rejected the latest appeal by Vietnamese victims who were suing the manufacturers of Agent Orange for billions in compensation. As an act of charity, Washington has offered a paltry $3-million not only to help treat the victims of America's biggest experiment with chemical-warfare tactics but to clean up the contamination that keeps adding to the toll.
The Vietnamese have suffered the most and received the least help, but they aren't the only victims. Agent Orange tainted everyone it touched, and so binds Vietnam not only to the United States, whose fighters also paid a price for the misery they created, but to Canada as well.
More than two decades after ailing U.S. veterans were awarded $180-million in compensation (in addition to the billions spent on their medical care), Ottawa is offering $20,000 each to an estimated 4,500 Canadian soldiers and civilians exposed when Agent Orange was secretly tested on a New Brunswick military base.
And just as Vietnam continues to press a stubborn U.S. government to help clean up the damage Agent Orange caused, a sleepy Ontario farming town is still struggling 40 years after the fact to rid itself of the fallout from a local chemical plant that brewed up millions of litres of the stuff for the U.S war effort.