(Amy Zegart, co-director of the Center for International Security and Cooperation, wrote the following essay for The Atlantic.)

Today The Washington Post dropped the bombshell that President Trump had revealed classified information about the Islamic State to Russian Foreign Minister Sergei Lavrov and Russian ambassador Sergey Kislyak when the three of them met at the White House last week. You know a story is big when it gets as many concurrent visitors as the story about the infamous Access Hollywood video. There was no hiding near bushes in the dark this time to walk back the damage. Deputy National-Security Advisor Dina Powell declared the story “false,” and the administration also called out the big guns, with Secretary of State Rex Tillerson and National Security Advisor H.R. McMaster dutifully rushing into the breach to discuss the breach, using oh-so-carefully worded statements about how the president did not reveal “sources or methods” or any “military operations” that were not already known publicly.

So just how bad is the damage? On a scale of 1 to 10—and I’m just ball parking here—it’s about a billion. The story, which has since been confirmed by The Wall Street Journal, The New York Times, Reuters, Buzzfeed, and CNN, notes that the president could have jeopardized a critical source of intelligence on the Islamic State. Not America’s source. Somebody else’s. Presumably from an allied intelligence service who now knows that the American president cannot be trusted with sensitive information.

The type of information Trump cavalierly shared fell under a classification known as “code word,” according to the Post. There are three basic levels of classified information. Confidential information is defined as anything that could reasonably be expected to “cause damage” to American national security if shared without authorization. Secret information is one step up, considered to have the potential to cause “serious damage” if revealed. Top Secret information is a higher classification level still, comprising anything that could reasonably be expected to cause “exceptionally grave damage” to U.S. national security if revealed.

Code word is beyond Top Secret. It limits access to classified information to a much narrower pool of people to provide an extra layer of security. Many secrets are super-secrets—Harry Truman, as vice president, didn’t know about the Manhattan project. He learned of it only after Franklin Delano Roosevelt died and Truman was sworn in as president. Code word classification is so far off the scale, even fake spies rarely refer to it in the movies. Technically, the president can "declassify" anything he wants, so he did not violate any laws. But as Lawfare notes, if the president tweeted out the nuclear codes, he also wouldn't violate the law—but he would rightly be considered unfit for office.

Did Trump reveal intelligence crown jewels or just boast about the fact that he liked diamonds? According to the Post he revealed information about a purported ISIS plot involving laptops. It’s likely, however, that Tillerson, McMaster, the Postand the Times are ALL correct: The president did not reveal sources or methods or military operations. But that doesn’t matter much if he gave away information that will enable the Russians to identify the source or the methods. It looks like he did, since according to the Post’s account he talked about the content of a specific plot, the potential harm, and the location of the city in the Islamic State’s territory where the allied state’s intelligence service detected it. It was almost everything except the GPS coordinates. The denials by Tillerson and McMaster are a classic case of intelligence super-parsing—saying things that are technically and narrowly true but may not be accurate at all. No spin can hide the fact that the breach was deadly serious and reckless in the extreme.

Then there’s the impact on America’s unnamed ally, whom the Post reported was already nervous about sharing such sensitive intelligence with the United States. It is difficult to penetrate the Islamic State, and there is a major risk that this breach will close down a vital source. It’s an even bigger deal in the big picture, potentially jeopardizing intelligence cooperation with other U.S. allies around the world. Trump already raised intelligence eyebrows when he turned his Mar-a-Lago dining area into an impromptu Situation Room after the North Koreans decided to launch a ballistic missile. The president and his aides used the lights on cell phones to illuminate field reports, in full view of resort dinner guests snapping photos. If you’re known as someone who cannot keep a secret, the world’s secret-keepers are not going to tell you much.

“Can you believe the world we live in today?” President Trump said, according to one official in the two Sergeis meeting. “Isn’t it crazy?”

Yes, Mr. President. It’s crazy.