When the Washington Post revealed late Monday afternoon that President Trump had casually disclosed highly classified intelligence to Russian Foreign Minister Sergei Lavrov and Russian Ambassador Sergey Kislyak in the Oval Office, the words that immediately began to buzz around Washington were shocking and unprecedented. Such a disclosure, it seemed, had no historical corollary.

But that’s not exactly true: Presidents have a long history of sharing intelligence information with allies, as well as with the American people. John F. Kennedy, Ronald Reagan, and George W. Bush, among others, all chose to divulge critical intelligence information at some point during their presidencies.

What makes Trump’s disclosure unique was the apparently spontaneous manner in which he did it. Rather than sitting down with the intelligence community to talk through the risks and benefits of disclosing such sensitive information, Trump seems to have just blurted it out in the middle of a conversation.

That, says former CIA officer David Priess, is what’s “unprecedented” about this situation. By contrast, he says, “the act of sharing sensitive intelligence with foreign governments is, in fact, common.”

Presidents, explains New York University historian Tim Naftali, are “unique in our system in that they have the power to release any kind of classified information” at will. And in the past, he says, presidents have done so for numerous strategic reasons, including to justify policy decisions.

But that seems not to be the case here. It’s not clear whether Trump had a well-thought-out strategic reason for disclosing the information he did. Which means that he may have now burned a source, endangered lives, and possibly led to future intelligence failures for no good reason other than wanting to flaunt to the Russians what “great intel” he gets.

Kennedy and the Cuban Missile Crisis

In the summer of 1962, the Kennedy administration learned that Soviet Premier Nikita Khrushchev had begun to install nuclear missile launch sites in the Cuban countryside.

By October of that year, the presence of those launch sites brought the United States and the Soviet Union to the brink of total war. After consulting with the intelligence community, the Kennedy administration chose to release top-secret aerial photographs of the missile fields that US spy planes had captured, in order to make the case to the United Nations, and the rest of America, that the presence of nuclear missiles just 90 miles off the coast of Key West presented an unprecedented threat to American security.

Reagan and the La Belle disco massacre

On April 5, 1986, a West Berlin disco called La Belle was bombed, killing two and injuring 230 others. The attack wasn’t random — the club was a favorite of American military personnel stationed in Germany. Ten days after the club attack, President Ronald Reagan bombed Libya.

To justify his actions, Reagan went on television and revealed to the country that the administration had intercepted and read encrypted Libyan messages proving that Libya was responsible for the carnage in Berlin. In a televised message from the Oval Office, Reagan stated:

Our evidence is direct; it is precise; it is irrefutable. We have solid evidence about other attacks Qaddafi has planned against the United States installations and diplomats and even American tourists. Thanks to close cooperation with our friends, some of these have been prevented. With the help of French authorities, we recently aborted one such attack: a planned massacre, using grenades and small arms, of civilians waiting in line for visas at an American Embassy.

George W. Bush’s shared intel briefings

David Priess notes that George W. Bush often brought foreign leaders into his morning intelligence briefings. These are highly classified daily rundowns of the critical national security issues happening around the world that are prepared specifically for the president by the nation’s top intelligence officials.

“He asked Tony Blair, the British prime minister, and the Japanese prime minister and the Spanish prime minister to join him in these briefings,” says Priess. But Priess says that according to former Bush Chief of Staff Andy Card, the president would always ask the intelligence community if they were okay with the foreign leader being in the room. “He didn’t say he would do this. He asked,” explains Priess.

And in November 2001, Vladimir Putin flew to Texas to stay with Bush at his ranch in Crawford. Bush asked the intelligence community if Putin could sit in on one of his morning briefings. “They scrambled for information that could be shared with Russians without damage,” says Priess. The briefing book that day was a “work of art,” Priess notes.

The bottom line is that while presidents have certainly chosen to reveal intelligence information to allies or even to the entire world, such decisions were never made lightly.

This week versus the past

Another big difference between these examples and what Trump just did, according to Naftali, is that in those cases it was “almost always our intelligence” that the president was sharing.

The information Trump shared with the Russians, on the other hand, was not American intelligence but so called “third-party” intelligence — that is, intelligence that another country collected and then shared with us privately.

But countries do this “with the explicit understanding that the US will not share that information with anyone else unless they say it’s okay,” writes my colleague Zack Beauchamp. “That’s because doing so could potentially endanger the lives of their spies out in the field.”

Naftali said that the incident, if true as reported, is a “huge gaffe” that sends a terrible signal to our allies that the administration is “not careful about secrets” and “not careful about alliances.”

“When you start sharing other people’s secrets, that’s a big deal,” Naftali says. “You don’t do that unless there is a major strategic reason, and almost always, you don’t do it unless you have permission.”

In the case of Trump, it seems he had neither.