The allegations were made during a report on "Operation Tailwind" broadcast by CNN on June 7, followed by a print report published in Time magazine under the dual byline of two CNN employees. But by early July, the network retracted the story.
"We studied scores of documents about 'Operation Tailwind,' and conducted interviews with soldiers and officials at all levels of command. We found no evidence to support the CNN/Time assertions on defectors or the use of Sarin nerve gas," Cohen said in a statement.
"No document - military order, after-action report, briefing paper or official military history - mentions pursuit of U.S. defectors as Tailwind's mission. While sarin was stored in Okinawa in 1970, we found no evidence sarin nerve gas was ever sent to or sued in Vietnam or Laos," Cohen said at the Pentagon.
All chemical agents stored in Okinawa during the Vietnam conflict were removed in 1971 prior to the reversion of the island to the government of Japan in 1972, the statement said.
"All Americans should know the 16 men who conducted this mission were heroes, but they have been hurt by this report," Cohen said.
In its June 7 report, CNN said U.S. Special Forces troops were put into Laos to locate and kill American defectors. It said the troops destroyed a village, and killed American defectors as well as enemy troops and civilians. U.S. aircraft dropped the sarin gas to suppress the enemy as the Americans were to be taken from the scene by helicopter, the CNN report alleged.
The Pentagon study said the operation was launched as a reconnaissance mission "to engage the enemy and to divert enemy attention" from "Operation Gauntlet," an offensive mission designed to gain control of terrain in Laos.
"No records or personal recollections were discovered to suggest that targeting U.S. defectors played any part in the operation," the report said.
On the allegations of sarin use, the report noted that U.S. policy since World War II had been to prohibit the use of lethal chemical agents, unless first used by the enemy.
"No evidence could be found that the nerve agent sarin was ever transported to Southeast Asia (Vietnam, Cambodia, Thailand)Â…No evidence could be found that sarin was used in Operation Tailwind," the report stated.
Air Force personnel involved in the mission have stated tear gas was used. The type of gas employed was designated CS, and more potent version than the CN tear gas previously used in the conflict, the Pentagon study said.
The report also stated that "relevant North Vietnamese military documents reviewed record no use of lethal chemical gents by U.S. forces at any time during the Vietnam War, but they do record the use of tear gas."
Cohen ordered a Pentagon investigation shortly after the story was broadcast, saying the charges were serious enough to warrant a probe even though initial studies found no evidence the gas was used.
In its retraction, CNN apologized for "serious faults" in its reporting and that a CNN-requested investigation by a prominent media attorney concluded that its joint NewsStand report with Time magazine could not be supported.
The report's two main producers, Jack Smith and April Oliver, were fired. Senior producer Pam Hill resigned, while the lead reporter, Peter Arnett, was reprimanded.
Smith and Oliver said they stood by the Valley of Death story.
"CNN alone bears responsibility for both the television reports and for the printed article in the June 15 issue of Time magazine," Tom Johnson, chairman of the CNN News Group, said in a statement issued at the time of the retraction. "We acknowledge serious faults in the use of sources who provided NewsStand with the original reports and therefore retract the Tailwind story."
The toxicity of sarin is such that had it been used to help retrieve soldiers, "it is highly improbably al 16 U.S. servicemen and all but three Montagnards would have survived the mission alive." The indigenous Montagnards forces were assisting the Americans in the operation.
Retired Adm. Thomas Moorer, a former chairman of the Joint Chiefs of Staff, was said in the report to have confirmed the use of the nerve gas, but only in an off-camera interview. However, he later said he had heard rumors but saw no direct evidence that the deadly chemical was used.
Written by Susanne M. Schafer