That said, the American government’s resistance to connecting the dots in any manner has melted away over the years. The Agent Orange Act of 1991 accepted a presumed link to illnesses like non-Hodgkin’s lymphoma, soft-tissue sarcoma and chloracne. Veterans with those ailments were declared eligible for medical treatment and financial compensation without having to prove they had been exposed to herbicides. Over time, more than a dozen other maladies, including Hodgkin’s disease and prostate cancer, were steadily added to this list.

And the story is far from over. Some veterans who never set boots on the ground in Vietnam are seeking compensation for their medical woes, among them sailors who served on ships off the Vietnamese coast and airmen who worked on possibly contaminated C-123s that were put to other uses after the war.

Perhaps no two people embodied the moral complexities and the agony of Agent Orange more graphically than Adm. Elmo R. Zumwalt Jr. and his son Elmo R. Zumwalt III. Admiral Zumwalt led American naval forces in Vietnam from 1968 to 1970, before he became chief of naval operations. He ordered the spraying of Agent Orange. The son was in Vietnam at about the same time as the father, commanding a Navy patrol boat. Years later, doctors found that he had lymphoma and Hodgkin’s disease. He died in 1988 at 42. His son, Elmo IV, was born with congenital disorders.

The older Zumwalts wrote about their experiences in a book, “My Father, My Son,” published in 1986 and later made into a television movie. Also in 1986, they collaborated on an article for The New York Times Magazine. The son could not scientifically prove that Agent Orange was responsible for his suffering and that of other veterans, he wrote in The Times. “But,” Elmo III added, “I am convinced that it is.” In no way did he blame his father. “I do not doubt for a minute that the saving of American lives was always his first priority,” he said. “Certainly thousands, perhaps even myself, are alive today because of his decision to use Agent Orange.”

For his part, Admiral Zumwalt, who died in 2000 at 79, wrote that even knowing what he had come to learn about the chemical’s effects, he “still would have ordered the defoliation to achieve the objectives it did, of reducing casualties.” All the same, he became a strong advocate for ailing veterans and the national obligation to compensate them. In 1990, he wrote a report on Agent Orange for the Department of Veterans Affairs. He also testified before a House subcommittee, strongly denouncing previous studies that described the chemical spray as harmless. “That was, of course, the conventional propaganda of the time,” he said.

There is no shortage of programs initially deemed essential, and safe, only to produce unwelcome consequences. To cite but one, American-hired pilots sprayed herbicides over coca-growing zones in Colombia, part of the so-called war on drugs. People in those regions later reported significant medical problems.

Who knows what will be discovered someday about the health of Americans who served multiple tours in Afghanistan and Iraq. But first, there is older business to tend to. The ‘60s, it seems, aren’t over yet.

CLYDE HABERMAN, a regular contributor to Retro Report, has been a reporter, columnist and editorial writer for The New York Times, where he spent nearly 13 years based in Tokyo, Rome and Jerusalem. Subscribe to our newsletter here and follow us on Twitter @RetroReport.

This article first appeared in The New York Times.