Updated

The National Security Agency (search) has been blocking the release of an article by one of its historians that says intelligence officers falsified documents about a disputed attack that was used to escalate the Vietnam War (search), according to a researcher who has requested the article.

Matthew Aid, who asked for the article under the Freedom of Information Act (search) last year, said it appears that officers at the NSA made honest mistakes in translating interceptions involving the 1964 Gulf of Tonkin (search) incident. That was a reported North Vietnamese attack on American destroyers that helped lead to President Johnson's escalation of U.S. involvement in Vietnam.

Rather than correct the mistakes, the 2001 article in the NSA's classified Cryptologic Quarterly says, midlevel officials decided to falsify documents to cover up the errors, according to Aid, who is working on a history of the agency and has talked to a number of current and former government officials about this chapter of American history.

Aid draws comparisons to more recent intelligence on Iraq's weapons of mass destruction that overstated the threat posed by Saddam Hussein's arsenal.

"The question becomes, why not release this?" Aid said of the article. "We have some documents that, from my perspective, I think would be very instructive to the public and the intelligence community ... on a mistake made 41 years ago that was just as bad as the WMD debacle."

The NSA is the largest spy agency in government, responsible for much of the United States' codebreaking and eavesdropping work. In spy lingo, the agency collects and analyzes "signals intelligence" — or "SIGINT."

The article, written by NSA Historian Robert Hanyok, and the controversy over its release were first reported in The New York Times on Monday.

In a written statement, NSA spokesman Don Weber said the agency had delayed releasing the article "in an effort to be consistent with our preferred practice of providing the public a more contextual perspective." He said the agency plans to release the article and related materials next month.

"Instead of simply releasing the author's historical account, the agency worked to declassify the associated signals intelligence ... and other classified documents used to draw his conclusions," Weber said.

Aid has been told that Hanyok's article analyzes problems found in interceptions about the events. He said the nature and extent of the mistakes remain unclear, and some senior officials at NSA who were not involved with the errors have taken issue with the journal article.

Many historians believe that Johnson would have escalated U.S. military action in the region anyway.

Yet Steven Aftergood, director of the Federation of American Scientists (search) project on secrecy, said events of the Cold War cannot remain off limits, effectively a secret history.

"A lot of what we think we know of our recent history may be mistaken," Aftergood said. "It is a disgrace that it should be so in a democracy, but it is."

James Bamford, who has written several books on the NSA, said the agency has a "lethargic attitude" about revealing historic information "that may be useful for people in the future, to help prevent mistakes."