US president Donald Trump ©Sipa USA/SIPA USA/PA Images

As an intelligence historian working in the Applied History Project at Harvard Kennedy’s School of Government, I study ways that history can inform present government intelligence and national security policies. One of the issues my colleagues and I are grappling with is the extent to which history remains relevant when something happens so dramatic, and damaging, that it fundamentally breaks with the past. I would look at this the other way round: during world-shaking crises, it is more important than ever to look to history, as past similarities and differences can help us better understand them. Events last week in Donald Trump’s White House have tested this theory to the extreme: they are without precedent in US history.

On Tuesday last week, Trump fired his FBI director, James Comey, who was heading a counter-intelligence probe into the president’s election connections with Russia. The next day, having “terminated” Comey, and given confusing explanations for doing so, Trump held a private meeting in the Oval Office with two top-ranking Russian diplomats, the Russian foreign minister, Sergei Lavrov, and the Russian ambassador in the US, Sergei Kislyak. During this meeting, Trump is understood to have disclosed to his Russian guests highly classified “code-word” intelligence—the highest classification intelligence in the entire US government.

To make matters worse, this intelligence was derived from a US ally, reportedly Israel. Never before has a US president unilaterally disclosed to a hostile power, Russia, ultra secret intelligence derived from a US intelligence ally without permission from that country. If the reports are true, we are now in historically uncharted territory. Trump’s disclosures to the Kremlin—pundits are calling it LeakGate—pose a serious risk to US national security. America and its intelligence allies are not equipped for a leaker-in-chief as president. No wonder Lavrov and Kislak are smiling in the pictures of their Oval Office meeting.

Trump’s well-respected National Security Adviser, HR McMaster, was sent out to deny press reports that Trump leaked classified intelligence to his two Russian visitors. However, apparently working at cross-purposes, in an early morning twitter storm, Trump appeared to confirm that he disclosed “facts” on terrorism and airline safety to the Russians for “humanitarian” reasons—adding that he had an “absolute right” to do so. Whether this is true legally misses something more important: the security, intelligence,…

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