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, 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 starting today, the 60th anniversary of the day Hiroshima, Japan, became the first city to suffer an atomic attack.

Its release on the Sundance Channel is the culmination of years of effort to bring the government footage before a large U.S. audience. It will be the most-extensive exposure yet of the 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 in the Pacific. The documentary was first released last year.

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.

"It was to me the most horrendous, terrifying thing I had ever seen," camera operator Herbert Sussan, who's now deceased, said in a 1983 interview with the British Broadcasting Corp. (BBC). "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 the work to the rest of the world was not easy. 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 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.

"I felt there was a need to tell this story," McGovern told the BBC for a 1983 report that used footage from the U.S. film project. "If it were not captured and shown to people, no one would ever know what happened."

McGovern and Sussan were appalled when their footage was kept from public view and used only for military-training videos. Over the years, Sussan repeatedly asked for its public release, appealing as high as President Truman and Robert Kennedy.

"Every time I sought to obtain the footage, I came up against a brick wall," he told the BBC.

Sussan, 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.