President Trump delayed the release of thousands of pages of classified documents related to the John F. Kennedy assassination on Oct. 26, citing concerns from the CIA, FBI and other federal agencies. (Joyce Koh/The Washington Post)

They’d been waiting 25 years to see the final — and potentially most sensitive — batch of records related to President John F. Kennedy’s assassination. Then came word late Thursday that President Trump had acquiesced to CIA and FBI lobbying to withhold tens of thousands of the files.

For historians, journalists and Kennedy buffs, the promise of revelations about what happened in Dallas on Nov. 22, 1963, disappeared.

“My expectations were low, and they should have been lower,” said Gerald Posner, author of the 1993 Kennedy assassination book “Case Closed.”

Though the National Archives and Records Administration put 2,800 records online, about 30,000 more remain concealed at the urging of national security officials.

On Friday, WikiLeaks offered $100,000 for the still withheld documents. On Twitter, the organization’s founder, Julian Assange, polled followers over President Trump’s about-face.

Latest release from the JFK assassination records

“Why did U.S. intelligence agencies fail to meet the legal deadline they had 25 YEARS NOTICE OF for the release of all remaining JFK files by today?” he asked. The choices: “Show power over Trump,” “Ruin Trump’s PR move,” “Serious incompetence” or “Conceal activities.”

Early Friday morning, the president tweeted assurances to those infuriated by the delay that he wants to disclose as much as possible: “JFK Files are being carefully released. In the end there will be great transparency. It is my hope to get just about every thing to the public!”

Trump followed up that message Friday evening with another tweet, saying, “After strict consultation with General Kelly, the CIA and other Agencies, I will be releasing ALL JFK files other than the names and addresses of any mentioned person who is still living. I am doing this for reasons of full disclosure, transparency and in order to put any and all conspiracy theories to rest.”

He did not say when he would release the remaining documents.

Peter Kornbluh, a Cuba specialist at the National Security Archive at George Washington University, said he, too, was frustrated because the government had 25 years to make the deadline imposed by the President John F. Kennedy Assassination Records Collection Act of 1992 . The law required that all the records “shall be publicly disclosed in full.”

But the act came with an asterisk, allowing the president to withhold documents beyond Oct. 26, 2017, if he decided disclosure would harm national security.

What happened when JFK was killed

“I have no choice — today — but to accept those redactions rather than allow potentially irreversible harm to our nation’s security,” Trump wrote in a memo Thursday night.

Many leading Kennedy experts weren’t buying it.

Kornbluh, the Cuba authority, said most of the papers that were released didn’t warrant the long-held secrecy. He pointed to a never-before-seen memo by Hoover, dated two days after the assassination. Hoover says in the memo that he wanted to have “something issued so we can convince the public that Oswald is the real assassin,” and that he thought the investigation should be kept secret because of Oswald’s contacts with the Cuban embassy in Mexico City and the Soviet Embassy in Washington.

“What is the secrecy around that document really about?” asked Kornbluh, who co-
authored a 2014 book on the United States’ secret diplomacy with Cuba called “Back Channel to Cuba.”

For Kornbluh, some of the more intriguing documents in the entire Kennedy collection were not released Thursday. He was hoping to see the files on Luis Posada Carriles , who had been given explosives training by the CIA as part of the Bay of Pigs invasion and was later implicated in several terrorist attacks.

“We could learn the degree to which he worked for the CIA, his operations and the whole history of how he left the CIA and went to Venezuela to plan the bombing of a Cuban airliner in 1976 that killed 73 men, women and children,” Kornbluh said.

He was intrigued by some released records Thursday, including a 1975 report by White House counsel Philip Buchen, who summarized the CIA’s assassination plots against foreign leaders. Some of the more eye-popping details included a proposed government operation to induce Cubans to overthrow their government, with financial rewards for various types of Cuban leaders: up to $100,000 for government officials, and perhaps for symbolic reasons, two cents for Castro.

“The price list appears to be new,” Kornbluh said. “I think it is one of the most comprehensive summaries of real and proposed assassination operations against Castro that I have ever read, and I have read all of them.”

Trump on Thursday gave intelligence agencies until March to propose which redactions they still want to preserve. By April 26, Trump will make another decision on what to release and what to withhold.

Rex Bradford, president of the Mary Ferrell Foundation, which collects documents on numerous government investigations, said he worries the six-month delay — after a 25-year wait — just makes it harder to suppress the rampant myths surrounding the murder.

“I am sure that withholding fuels conspiracy theorists,” Bradford said. “At the same time, we have some sympathy for agencies who would rather not reveal sensitive or embarrassing information. In some cases, those are legitimate positions. But many others feel like, at this point, the public interest far outweighs those concerns.”

The material proved daunting to media organizations, amateur sleuths and experts alike. Each agency has its own language of acronyms and euphemisms that take time to learn.

Often, seemingly simple terms are deliberately misused, wrote Greg Bradsher, a senior archivist at the National Archives at College Park, in a blog. A “highly reliable informant” could actually be a microphone. “Special” or “sensitive investigative techniques” could be code for break-ins. And illegally obtained dirt could be disguised as information from a “confidential informant.”

The Hoover memo drew the most attention from media outlets and on social media. Hoover said the FBI had repeatedly warned Dallas police about threats against Oswald in the hours after Kennedy’s assassination.

“Last night we received a call in our Dallas office from a man talking in a calm voice and saying he was a member of a committee organized to kill Oswald,” Hoover reported. “We at once notified the chief of police and he assured us Oswald would be given sufficient protection. This morning we called the chief of police again warning of the possibility of some effort against Oswald and again he assured us adequate protection would be given. However, this was not done.”

The Miami New Times found a memo discussing a false-flag operation that never came to fruition. According to the memo, the CIA considered creating a false “Communist Cuban terror campaign” to turn the public against the Cuban Revolution. “We could sink a boatload of Cubans en route to Florida (real or simulated),” an official wrote. “We could foster attempts on lives of Cuban refugees in the United States even to the extent of wounding in instances to be widely publicized.”

British media jumped all over an FBI file claiming that a local newspaper, the Cambridge News, had received a tip about “some big news” in the United States shortly before the assassination.

“The caller said only that the Cambridge News reporter should call the American Embassy in London for some big news and then hung up,” CIA counterintelligence chief James Angleton wrote to Hoover. “After the word of the President’s death was received the reporter informed the Cambridge police of the anonymous call and the police informed MI5. The important point is that the call was made, according to MI5 calculations, about 25 minutes before the President was shot.”

The paper reported Friday it had never been able to figure out whether the call was made.