The National Security Council was created 70 years ago, at the dawn of the Cold War, as the White House intelligence center – where secrets of state were weighed, assayed and placed before the president for life-and-death decisions.

U.S. National Security Advisor Michael Flynn (R) and Senior Counselor Steve Bannon board Air Force One at West Palm Beach International airport in West Palm Beach, Florida U.S., February 12, 2017. REUTERS/Carlos Barria

Running the NSC is a killing job. You juggle hand grenades seven days a week. Keep them flying and you gain great power, like Henry Kissinger did. Let them fall and you might face indictment like the two NSC chiefs who blew covert operations under President Ronald Reagan.

Twenty-five people have held the post. Never has there been one like Michael Flynn, the former lieutenant general appointed by President Donald Trump. Flynn has been under investigation by the FBI since late last year – and that is a danger to American national security.

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Flynn has been startling superiors and subordinates since he became director of the Defense Intelligence Agency in 2012. He had spent a brave decade on the dark side of the war on terror. But he flouted authority and flayed his counterparts in the national security establishment, flaunted what DIA officers called “Flynn facts” – falsehoods – such as asserting that Iran has killed more Americans than al Qaeda in the 21st century, and was fired in 2014.

Then, as a private citizen running an intelligence consulting firm, Flynn got cozy with Russian President Vladimir Putin. After dining as Putin’s guest of honor and taking payments from his propaganda machine, Flynn got on the Trump bandwagon, tweeting links to fake news accusing Hillary Clinton of sex crimes with children and leading “Lock Her Up!” chants at raucous rallies. His reward was his appointment as national security adviser. He took office on Jan. 20 – already the subject of scrutiny by FBI counterintelligence agents and their colleagues at the CIA. The case is the most politically charged intelligence investigation since the Cold War.

The FBI and the CIA agree that Putin tried to swing the 2016 election for Trump. (Trump concedes that point but says he had nothing to do with Putin’s efforts.) The intelligence agencies reached this conclusion in December: cyber-attacks, information warfare, and clandestine operations promoted Trump as part of a campaign to destabilize Western democracies. That fact beggars belief, but American, British and German intelligence services are unanimous about Putin’s astonishing ambitions.

The explosive question for the FBI is whether members of the Trump campaign were in cahoots with this covert crusade on behalf of their candidate.

Enter Flynn – as a private citizen, before his swearing-in, and a subject of the FBI’s scrutiny – conversing with Sergey Kislyak, the Russian ambassador to the United States. These colloquies, as Reuters reported on Jan. 13, included five talks in late December. They began just before Obama hit back hard at Moscow for meddling in the election, targeting 35 Russian intelligence operatives, and continued until Putin’s surprising statement that he would not respond tit-for-tat.

The FBI listened in; the Bureau and American intelligence have routinely eavesdropped on foreign embassies in Washington since the 1950s.

Was it wrong for Flynn to talk with the Russian envoy? Absolutely not. Kissinger himself met with Boris Sedov, officially a diplomat but actually a spy, at the Soviet Embassy on Jan. 2, 1969, eighteen days before President Nixon was inaugurated and Kissinger became his national security adviser. “Sedov said that the Soviet Union was very interested that the inaugural speech contain some reference to open channels of communication to Moscow,” Kissinger told the president-elect. Nixon took that to heart at his swearing-in. His exact words, addressed to Moscow: “Our lines of communication will be open.”

The difference between then and now? Kissinger checked in with FBI Director J. Edgar Hoover before he went to talk to Sedov. In the context of the Cold War, that constituted the highest security clearance.

Flynn did not clear his chats with Putin’s ambassador – certainly not with the FBI nor the Obama administration, and evidently not with the incoming secretaries of state and defense, who are statutory members of the National Security Council. That might be no more than a diplomatic misdemeanor.

But it might be something worse. Flynn insisted until late last Thursday that he never talked about the sanctions to Moscow’s man in Washington. When he learned that the FBI had proof to the contrary, on tape, Flynn contradicted himself, saying he couldn’t recall what he had said. Every national-security reporter in Washington has that story nailed. Their work has the acrid odor of truth, still smoldering.

It’s a big if, but if Flynn presents falsehoods face-to-face with the FBI, it’s a potential felony.

Or Flynn’s troubles may vanish in the swamp. Remember Kissinger’s deathless quip, which Trump’s Supreme Court nominee Neil Gorsuch chose as his college yearbook epigraph: “The illegal we do immediately. The unconstitutional takes a little longer.” Kissinger survived a scarifying stint at the National Security Council, won the Nobel Peace Prize while denounced as a war criminal, and, at age 93, reigns as an eminence grise. Michael Flynn is a tough guy. He might live to fight the long game under President Trump.

(Tim Weiner is a Pulitzer Prize-winning reporter. His books include Legacy of Ashes: The History of the CIA.)