The memory wears on J. Preston Truman like a cowboy's brand. Searing, immovable, unforgettable.

It was about 1953, and Truman — "J" to his family and friends — was nestled in his father's arms on the porch of the family home in Enterprise, a small southern Utah ranching hamlet of about 800. It was sometime just before dawn when the western sky erupted in white light.

He was only 2 1/2, maybe 3 years old at the time, but he was old enough to sense fear. He didn't, he couldn't comprehend that he had just become a frontline witness to an above-ground nuclear test at the Nevada Test Site less than 100 miles away, or that it would change his life forever.

"It scared . . . me," said Truman, who traces his storied career as an anti-nuclear activist to that impressionable childhood experience.

Today, Truman, now 49, is the venerable head of Utah Downwinders, a loose-knit montage of Quixotic gadflies who for three decades have campaigned to end all nuclear testing and to arrive at some sort of justice for countless thousands — many in Utah and Nevada — who have been killed and maimed by the nation's Cold War nuclear legacy.

It is a toxic legacy that still haunts native Utahns, most of whom know someone — a family member, a friend, a neighbor — who has suffered from diseases believed linked to radiation poisoning inflicted by their own government.

Truman was only 4 years old when his first friend, 5-year-old Michael Stalie, died of leukemia. Within a year or two, four other children in nearby Parowan and Paragonah had died of leukemia. Then grown-ups started getting the disease.

"Suddenly it was leukemia, leukemia, leukemia everywhere you looked," he remembers.

Still, most living in Mormon communities scattered throughout southern Utah and Nevada remained fiercely patriotic in the 1950s and 1960s. To question the government was to raise suspicions about loyalty, or worse to conjure up accusations of being a Communist sympathizer.

Truman remembers a well-orchestrated propaganda campaign by the U.S. government to assure local residents that the nuclear tests were safe and blaming the Soviets for everything from poisoning the air to stranding a helpless dog in space.

"There was kind of a carnival atmosphere about the whole thing," he said. "As kids, we would go out and play atomic war."

They didn't know it, but it wasn't a game. There were days the radioactive fallout from nuclear blasts settled so thick on the family's 1951 Ford that Truman could write his name in the white ash.