When the Washington Post first reported that that President Donald Trump disclosed classified information in a meeting with Russian Foreign Minister Sergei Lavrov, it was difficult to even process what was happening. The president did what? With whom?

But since the story broke Monday afternoon, a consistent through-line began to emerge as to what had happened. The president, seemingly on a whim, gave a US adversary closely held information about an ISIS threat that had been provided by a US intelligence partner.

Making things even more complicated, the New York Times reported Tuesday that the original source of the classified information was Israel. That seems certain to cast a pall over Trump’s trip to Israel next week, especially since Israeli spies have worried for months that information given to the Trump administration would find its way first to Russia and then Iran, a Kremlin partner that also happens to be Israel's biggest enemy.

This is a staggeringly severe breach, one that experts on the intelligence community warn could jeopardize US national security for the foreseeable future — even directly putting lives on the line.

Understanding why this is such a big deal can be tough. It requires a deep attention to detail about what literally happened, to the point of parsing specific word choices by the Trump administration. It also requires understanding a lot of obscure intelligence jargon and practices, like the details of foreign intelligence sharing.

What follows is a user-friendly guide designed to answer the four biggest questions swirling about the Trump breach: What literally happened, why it’s a big deal, whether Trump broke the law, and how, if it all, he might suffer consequences for his actions.

The bottom line? Trump did it, it’s dangerous, and there’s nothing to stop him from doing it again so long as he remains president.

What actually happened?

There’s a lot of confusing information swirling about this — including from the White House itself. But the Washington Post’s original story, by Greg Miller and Greg Jaffe, is still the best point to start with. Here are the core points it hits:

Trump disclosed the information in an Oval Office meeting with Lavrov on May 10. Russian Ambassador to the US Sergey Kislyak (yes, that Sergey Kislyak) was also there.

The information Trump revealed to Lavrov concerned information about an ISIS plot to bomb airplanes using laptops.

Revealing it “jeopardized a critical source of intelligence on the Islamic State,” according to the Post — specifically by giving the Russians enough information about the nature of the source to easily identify who or what it is.

That intelligence came from “espionage capabilities of a key partner,” per Jaffe and Miller, that we now believe to be Israel. The information allegedly provided by the Israelis was so sensitive that it wasn’t being shared with any other allies.

The gaffe — something unprecedented in recent American history — seems to have been the result of Trump bragging about the quality of his intelligence. “I get great intel. I have people brief me on great intel every day,” the president reportedly said.

These basic details essentially have been confirmed by a number of other outlets — including the New York Times and the Wall Street Journal. The basic contours seem pretty clear.

Top White House officials, most notably National Security Adviser H.R. McMaster, have called the story “false.” But if you parse their statements more carefully, you see that they’re not actually responding to the Post’s story.

In both a written statement and a Tuesday press conference, McMaster was very careful to say only that the president hadn’t compromised “sources and methods.” In intel-speak, that means the president didn’t directly tell the Russians who or what were the sources of the intelligence on ISIS or the method by which it was gathered (human spies, communications intercepts, drone imagery and the like).

But the Post and other outlets never said that the president disclosed sources or methods directly. Instead, they reported that the president gave away enough classified information that the Russian could easily figure out the sources and methods on their own.

“Trump revealed the city in the Islamic State’s territory where the U.S. intelligence partner detected the threat,” Miller and Jaffe write. “The identification of the location was seen as particularly problematic, officials said, because Russia could use that detail to help identify the US ally or intelligence capability involved.”

No White House official has denied this aspect of the Post’s reporting. They appear to be playing, as Jaffe put it in an MSNBC appearance, “word games” — setting up a fake version of what the Post alleged, that Trump directly disclosed sources and methods, and then knocking that down.

In fact, the White House spin — particularly during McMaster’s Tuesday presser — ended up confirming some key aspects of the Post’s story.

“He [McMaster] confirmed that the president made an impulsive, unvetted decision to share info without even being aware of its source,” Julian Sanchez, an expert on privacy and surveillance at the libertarian Cato Institute, tweeted. “In other words: No review of the equities, no input from agencies on whether sources/methods could be reverse engineered.”

And it’s this “reverse engineering,” as Sanchez put it, that’s been the problem the whole time.

How bad is this?

“On a scale of 1 to 10 — and I’m just ball parking here — it’s about a billion,” Stanford professor Amy Zegart wrote in the Atlantic, in answer to that very question. “The breach was deadly serious and reckless in the extreme.”

Zegart is right. This will have a direct and tangible effect on US security.

It’s easy for us to think that the United States gets most of its intelligence from CIA spies, satellite photos, or NSA intercepts. The truth, though, is that the US relies heavily on exchanges with partners in foreign intelligence services — like Israel’s Mossad — especially when it comes to ISIS and other terrorist groups. The US depends vitally on its partners in the Middle East to get inside of those groups and figure out what they’re planning.

“As a matter of geography and language and culture, they are closer to the problem,” says Paul Pillar, a 28-year CIA veteran who worked on counterterrorism and the Middle East. “So they’re better able to collect against groups than we are.”

Given the magnitude of Trump’s breach, this will almost certainly lead the partner in question, Israel if the Times is right, to least temporarily suspend intelligence sharing with the United States.

That’s especially likely since it was Russia that Trump leaked to: The Israelis are deeply concerned about intelligence getting to the Iranians, and given that Russia is working closely with Iran to prop up Bashar al-Assad in Syria, there’s a very real risk that anything that gets to Moscow could end up in Tehran.

That is very bad. The Mossad is one of the world’s most effective and respected intelligence agencies, with a particular interest in Islamist terrorism. This coming just days before the president is traveling to Israel is … exceptionally awkward. The only silver lining is that Israel is less likely than some other partners, like Turkey, to keep the information channels between the US and their country closed for a long time.

What’s more, the Israelis appeared to have information in this case about an ISIS plot against flights inbound to the United States — information that, at least in theory, might have already saved lives. It’s possible that when the next ISIS threat comes up, the Israelis won’t share that information with the United States.

The breach also comes at a vital time for the ISIS fight. As the group continues to lose territory on the ground in Iraq and Syria, it will become harder to find ISIS terrorists as they blend into the population rather than fight openly to hold on to its “caliphate.” This makes it harder to get intel on the group’s activities, including international terrorist plots. So Trump may have just temporarily deprived the US of a source of vital information at an extremely important point in time.

And the implications go beyond Israel. The president has just shown that no foreign country, anywhere, can depend on the United States. Other allies — in Europe and East Asia as well as the Middle East — will wonder if the same thing will happen to them, and how much they can risk telling the United States at all.

The information Trump revealed was reportedly “code word” — the highest level of classification there is in the US government, one that hides it even from most people at the upper levels of the administration.

Yet it still got out, because the person at the top of the food chain is at best careless and at worst living up to preelection fears that he would give away too much to Moscow.

“It indicates utter disregard, or utter lack of knowledge, at the very top,” says Pillar. “Foreign partners will say, ‘My goodness, even if we’re given assurances of how carefully our information will be used — as long we’ve got this guy at the top who does this sort of thing, those US assurances don’t mean very much.’”

Hence why intelligence experts are so perturbed. Trump has committed a cardinal sin in the intel world, one that could jeopardize a major foundation of American power and security: its close cooperation with allies.

“It’s a disqualifying act,” Glenn Carle, another former CIA officer, tells my colleague Sean Illing. “People who do things like this in the CIA, at low levels, where everything is fraught with possible life-and-death consequences, are brought home immediately.”

Is what Trump did legal?

The line from the president’s defenders in the conservative media is that it was completely within Trump’s legal rights to disclose whatever information he wanted to. That’s the defense the president himself went with in a series of tweets on Tuesday morning:

I have been asking Director Comey & others, from the beginning of my administration, to find the LEAKERS in the intelligence community..... — Donald J. Trump (@realDonaldTrump) May 16, 2017

...to terrorism and airline flight safety. Humanitarian reasons, plus I want Russia to greatly step up their fight against ISIS & terrorism. — Donald J. Trump (@realDonaldTrump) May 16, 2017

Generally speaking, this is correct. In a very technical legal sense, the entire system of classification is set up under the president’s authority — the president is assumed to have access to anything he wants to see, and then sets up a system for how others can gain access to said information.

Therefore, President Trump is generally assumed to be able to declassify whatever he wants. Typically speaking, there’s a process for declassifying information when the president wants to. But the mere act of a president saying something that’s classified publicly — or, say, to the Russian foreign minister — can also change its classification status.

Not every expert shares that interpretation in this case. Steve Vladeck, a national security law expert at the University of Texas, thinks that “inadvertently” disclosing sensitive information is still a crime — even if it’s the president who discloses it.

“Legally, several of the key statutes don't prohibit disclosure of ‘classified’ info, but of info ‘relating to the national defense,’” Vladeck tweets. “It may very well be unlawful even for a sitting president to disclose certain types of classified information.”

Ultimately, though, this entire debate is a red herring. As Vladeck notes, no one is going to prosecute Trump even if his argument that Trump committed a crime is correct. It’s actually unclear if prosecutors even could go after Trump as long as he’s in office: The two times the DOJ has examined this question, in 1973 and 2000, it concluded that it would be unconstitutional to prosecute a sitting president.

And more fundamentally, the issue here isn’t whether the president broke some obscure statute. It’s whether the president’s personal qualities — his need to brag, his lack of knowledge about how the government works, his chumminess with Russia — led him to act in a way that put US national security at risk. That’s a serious scandal whether or not it’s illegal.

So while it’s very possible that Trump had the legal authority to do what he did, it’s the wisdom — not the legality — of his actions that are the question.

So what happens to Trump now?

Nothing major, unless Republican leaders in Congress want it to.

In terms of more serious punishments, the truth is that the US legal system provides very limited remedies for presidential misconduct, even for something as grave as this. The only real remedy is impeachment, a congressional move that would actually remove the president from office.

Some experts think this is serious enough to warrant that. “Any patriotic civil servant should take steps immediately … to remove the man from office,” Carle says.

But whether or not Carle or most anyone else agrees with that is irrelevant. The key question is whether the Republicans who control Congress — most notably Speaker of the House Paul Ryan and Senate Majority Leader Mitch McConnell — do. The answer appears to clearly be no.

My colleague Tara Golshan has been tracking Republican responses on Capitol Hill, and what she’s heard has been pretty lukewarm. Several Republicans have issued statements expressing “concern” about Trump’s actions, but none have proposed even coming close to impeachment. McConnell could only bring himself to express frustration with the “drama” coming out of the White House.

If impeachment isn’t on the table — and it clearly isn’t — then we’re basically stuck with the risk of this happening again and again for the foreseeable future. The intelligence community may attempt to limit Trump’s access to sensitive information, as it was reported to be doing earlier in his presidency, but the president can’t be kept out of everything.

And since the president himself — his own personal qualities — are the source of the security breach, the risk of it happening again simply cannot be ruled out or fully mitigated. We just have to live with the knowledge that an irresponsible man has access to the nation’s more valuable secrets, and the ability to reveal them as he pleases.

“Bottom line: It matters who we have running the most powerful institution in the world,” a group of experts at the national security site Lawfare write.

I’m inclined to agree. And that, in just a sentence, is the scariest part of this entire saga.