For at least seven years, it's been publicly known that 12 days before Red Chinese troops poured over the Korean borders, the CIA issued an intelligence estimate flatly predicting that wouldn't happen. But the original 56-year-old document has been reclassified and taken out of public view sometime in the last seven years _ one of more than 55,000 pages of previously declassified documents that have been swept from the shelves of the National Archives and removed from public scrutiny.

Intelligence historian Matthew Aid ridiculed government efforts to put a secrecy stamp back on the documents, noting that it took a laborious process of review to get the papers declassified in the first place.

He noted that that many of the documents reclassified at the National Archives were published in scholarly articles, copied on microfilms and distributed to libraries across the country _ or even published by the U.S. government itself in the official series "Foreign Relations of the United States."

"It's silly to reclassify at this point _ the screeners should have known that," Aid said. He said the CIA employed spies nearing retirement age as screeners, and they seem to have employed Cold War judgments in deciding whether some documents should be public.

"It's just a massive waste of money," and seems justified only to hide CIA blunders, he said.

The National Security Archives, a private organization associated with George Washington University, has assembled a partial list of the reclassified documents and concludes that many appear banal. One withdrawn document involves agrarian-reform programs in Guatemala from 1945 to 1956, while another is concerned with highway transportation in the Soviet Union after World War II.

Also reclassified were translations from a Soviet encyclopedia and documents involving official U.S. government foreign travel in 1959. And a withdrawn 1949 document involves the CIA's admission that the intelligence community's knowledge of Soviet weapon research and development was poor.

The disappearing documents at the National Archives are just part of a pattern of activities across the U.S. government in recent years.

In the wake of the 9/11 attacks, government Web sites have been scrubbed of any materials that might be of assistance to terrorists _ from architectural designs of aged bridges, to maps of high-pressure gas lines, information on plant and animal diseases, and the layouts of nuclear-power plants. Additionally, the Justice Department has instructed government agencies to take the strictest interpretation under the Freedom of Information Act to withhold any information that might damage the security of the homeland.

Secrecy News, a weekly publication of the Federation of American Scientists assembled by researcher Steven Aftergood, has tracked the withdrawals. In the latest disclosure, the Civil Air Patrol, the civilian arm of the U.S. Air Force, announced in January that it will no longer publicly disclose the radio frequencies it uses because such information is now judged to be "sensitive but unclassified" information.

All of that material is being added to the pile of papers marked with secrecy stamps that end up in National Archives vaults, waiting to be declassified. More than 15.6 million documents were classified in 2004 alone _ an 80 percent increase over the number of documents stamped secret in 2001, and costing more than $7 billion to store.

In 1995, President Bill Clinton issued an executive order directing the Archives to declassify en masse all documents more than 25 years old. Clinton's order has exemptions for very sensitive documents _ for example, material that might disclose the identities of CIA informants, or explain how to build a nuclear bomb.

The deadline for completing that declassification is December, but Archives spokeswoman Susan Cooper said the schedule has been disrupted by the issue of reclassifying previously declassified documents.

Archivist Allen Weinstein has ordered a moratorium on any further documents being withdrawn from public view, and asked for new guidelines to be written concerning any further withdrawals. Weinstein said he's also ordered an audit to come up with a complete list of documents withdrawn.

Cooper said staff involved in the declassification of 25-year-old documents have been diverted to complete the audit.

"This program is only going to slow us down," she said. "Since 1995, we've declassified 1.4 billion pages, and that's huge. But we've got a lot more to go through."