Washington ? Sixty years after the United States dropped two atomic bombs on Japan, a film documenting the aftermath is reminding Americans about the horrors of nuclear war.

Footage from a U.S. government-produced film, which was labeled top secret and kept out of public view for decades, is included in “Original Child Bomb,” a documentary that will air on many cable stations Saturday, the 60th anniversary of the day that Hiroshima became the first city to suffer atomic attack.

Its release on the Sundance Channel is the culmination of years of effort to bring the government footage before a large American audience. It’s the most extensive exposure yet of this long-suppressed footage in the United States. Some anti-war activists see the film’s appearance on cable television as a crucial step toward an open discussion about the controversial bombings that ended World War II.

The young soldiers who shot the film in Hiroshima and Nagasaki less than a month after the dawn of the atomic age were unprepared for what they found.

People pray in front of the cenotaph dedicated to atomic bomb victims at the Peace Memorial Park in Hiroshima, western Japan, as Hiroshima marks the 60th anniversary of the city's bombing.

“It was to me the most horrendous, terrifying thing I had ever seen,” camera operator Herbert Sussan, now deceased, said in a 1983 interview with the British Broadcasting Corp. “I finally convinced myself and some of these people that there was some value for the rest of the people of the world to see what had happened in this first bombing.”

Showing their work to the rest of the world was no easy task. The nine hours of film, shot in color, captured horrifying scenes of destruction and human suffering, including a woman with the pattern of her dress burned onto her back and the shadows of vaporized civilians burned into walls.

U.S. government officials deemed it too sensitive to release. They also confiscated black-and-white footage that a Japanese film crew shot before the Americans arrived.

When Lt. Col. Daniel McGovern, the head of the U.S. film crew, learned about the Japanese crew’s earlier effort to document the carnage, he was able to obtain their film and lobby successfully to hire some of them for his project.

Sussan, who was 24 when he went to Japan, paid a personal price for his involvement in the project. Like many of the people he filmed, he developed lymphoma, a form of cancer, and died in 1985. He wanted his ashes to be spread at ground zero in Hiroshima, but when his daughter traveled there a year later to fulfill his wish, she was told that it would be illegal.

Erik Barnouw, a film historian, created a moving 16-minute montage from the Japanese footage that screened in New York for the news media; all three major TV networks rejected it. Editorials criticized the move, and on Aug. 3, 1970, a public broadcast station aired the short to mark the 25th anniversary of the bomb. It would be nearly 10 more years before the American footage would emerge.

Greg Mitchell, who detailed the story behind the Hiroshima footage in a recent issue of Editor & Publisher magazine, said the postwar movie should be part of any debate about nuclear war.

“These guys weren’t anti-nuclear, they were for frank showing of what the truth was,” he said of Sussan and McGovern. “It’s the right of people to see what’s done in their name.”