On Wednesday, the US government released 1,491 previously secret documents concerning the assassination of President John F Kennedy in 1963.
Most Americans, and many people around the globe, have never believed the official report of the Warren Commission that JFK was killed by Lee Harvey Oswald, an unbalanced former US marine, acting alone without any help.
Indeed, of all the unresolved mysteries of the 20th century, JFK’s death is the one where the border between conspiracy theory and reasonable speculation is thinnest.
The new documents seem likely only to deepen that darkness, with many of them already released in partial, redacted form. Nevertheless, they provide fascinating insights into how the CIA, the KGB and others around the world reacted to the assassination.
Here are the most interesting revelations so far contained in the documents.
Oswald had contact with a 'KGB assassination agent'
The biggest revelation so far is the claim that Lee Harvey Oswald met with an agent of the Soviet Union's top-secret assassination unit about two months before Kennedy's assassination.
On 1 October, CIA agents in Mexico intercepted a phone call to the Soviet Embassy in Mexico City from a man speaking "broken Russian", who introduced himself as Lee Oswald.
"Hello, this is Lee Oswald speaking," says Oswald in the CIA's transcript. "I was at your place last Saturday and spoke to a consul. and they said that they'd send a telegram to Washington, so I wanted to find out if you had anything new? But I don't remember the name of that consul." The operator then suggests that it was Kostikov, which Oswald confirms.
Kostikov was a familiar name to the CIA. According to a memo dated 23 November 1963, one day after Kennedy's death, Kostikov was a member of the KGB's secretive 13th Directorate, "responsible for sabotage and assassination", who had given orders to an American double agent in a previous sabotage plot.
"Of course it is not usual for a KGB agent on a sensitive mission to have such overt contact with a Soviet embassy," the CIA wrote. However, it quoted top secret documents describing KGB doctrine that suggested it was sometimes possible.
To complicate the picture, the FBI told the CIA that they believed Oswald had been seeking the Soviet embassy's help with a "passport or visa matter". In any case, he drove back into the US via Texas later in October.
Australian ‘prank calls’ claimed knowledge of the killing
CIA agents were naturally curious when, in the days following the assassination, the US Department of the Navy informed them that it had received an anonymous tip-off predicting Kennedy’s death more than a year beforehand.
The details were... interesting. On 15 October, 1962, a man claiming to be a Polish chauffeur for the Soviet Embassy in Canberra, Australia, had called the US naval attache there and claimed that "Iron Curtain countries" had put out a $100,000 bounty – about $920,000 (£696,000) in today’s money – to kill President Kennedy.
The caller wasn’t very specific about who was behind it, though: "Communist men in England, Hong Kong, and probably some other countries." He also claimed that five Soviet submarines were carrying 400 to 500 Soviet soldiers to Cuba in order to somehow support the governor of Mississippi (where Kennedy had recently deployed federal troops to suppress racist violence).
"It should be noted that the CIA had not previously known of the 1962 phone call," a later CIA memo said.
One year later, after Kennedy’s death, the man called back. He claimed he had been there in early November when the Soviets dispatched an Australian man to the USA carrying a briefcase, before engaging in sustained conversation over the radio. After the killing, he said, the Soviets in the embassy had toasted with vodka and said "we achieved what we want".
Australian authorities were sceptical, saying that Soviet offices in the country only used Soviet chauffeurs and that there was no record of the licence plate quoted by the caller (although he had also said the Soviets changed their licence plates often).
By May 1964, the CIA’s deputy director of plans, Richard Helms, concluded: "Available evidence would tend to show that the caller was some type of crank. This conclusion, however, cannot be confirmed."
The Australians agreed, perhaps explaining why they did not originally think the 1962 call would be of interest to the CIA.
CIA suspected Cuba might be involved
The documents show US intelligence officers investigating several possibilities involving Cuban leader Fidel Castro, including whether Oswald might have visited the Cuban consulate.
A Cuban embassy employee in Mexico City had been arrested by Mexican authorities and claimed that he had seen Oswald at the embassy. However, a Nicaraguan man later confessed to inventing this idea because he wanted to push the US into overthrowing Castro.
Another line of inquiry concerned whether Oswald might have been influenced by Castro, with or without Castro’s knowledge. A number of US newspapers had published stories about Castro’s claim that US leaders would be in danger if they attempted to remove him.
However, a memo in 1975 concluded: "Credible evidence that would [show Cuban or Soviet involvement] did and does not exist in Washington. But such evidence could exist in Moscow and/or Havana, whose voluntary inputs to the Warren Commission were minimal in quantity and quality... therefore, the belief that there was Soviet and/or Cuban connection with Oswald will persist and grow until there has been a full disclosure by these governments."
This theme of unreliability looms large in many of the documents, which are riven with uncertainty over whether sources can be trusted. For instance, a Russian defector named Nosenko told detailed tales about having overseen monitoring of Oswald when he briefly defected to the Soviet Union between 1959 and 1961.
Nosenko’s story details how the KGB was alarmed by Oswald’s suicide attempt after being told he could not stay in the country, and concluded that he was of no use to the agency because "he was not an interesting person and wasn’t normal". Yet other documents show the CIA doubted Nosenki’s credibility due to flaws and inconsistencies in his claims.
Incidentally, the documents do provide solid details of one government-sanctioned assassination plot – namely, by the CIA against Castro. "The first seriously-pursued CIA plan to assassinate Castro had its inception in August 1960," a memo recounts. "It involved the use of members of the criminal underworld with contacts inside Cuba..."
'I call BS'
JFK researchers expressed disappointment and frustration about the documents after their release on Wednesday. Larry Sabato, a leading expert at the University of Virginia, told CNN that the latest release was "minimal and worthless".
More than 10,000 documents still remain forbidden or redacted by the US government, and Mr Biden’s order will not mandate their disclosure until at least 22 December. Researchers say the government is stoking conspiracy theories by dragging its feet.
"It’s always ‘the next time,’" said Mr Sabato. "The reason it’s so important is not so much that we’re going to find a smoking gun that changes the entire theory of who killed Kennedy. The lack of transparency and the fact that getting these documents after 58 years is like pulling a whole mouthful of teeth. It tells you why we have so many conspiracy theories."
Another researcher, Larry Schnapf, announced he would sue Mr Biden’s administration, saying: "We will be seeking a court order instructing the President to release the remaining records or to disclose the specific identifiable harm posed by each document sought to be postponed and how such alleged harm outweighs the strong public interest in the release of these records."
Meanwhile, members of the QAnon movement, many of whom believe that Kennedy’s son JFK Jr did not die in a plane crash in 1999 but is actually alive and in hiding, were unimpressed by the disclosures.
"Haha! Convenient timing. It’s like they aren’t even trying," said one commenter under a news post about the documents on the encrypted chat service Telegram. "I call BS on it," said another. "Harvey Oswald was set up. The deep state is responsible."
Most took the view that the documents concerning possible KGB involvement were a feint designed to distract from the truth. "They blame Russia because they do not want us to know it was a three letter agency," said one post.