In the final days of Donald Trump’s administration, U.S. Gen. Mark Milley, the chairman of the Joint Chiefs of Staff, offered some very unusual instructions to senior military officials. If they received orders to launch an attack, up to and including the use of nuclear weapons, they were to "do the process” of consulting with him first. The general asked all of the officers to verbally signal their assent, which he reportedly considered "an oath.”

That’s according to a new book by Bob Woodward and Robert Costa. Milley had become so alarmed at Trump’s addled behavior, the authors say, that he felt the added safeguards were necessary to forestall a calamity. In issuing the orders, he knew full well that he was "pulling a Schlesinger,” or echoing the actions of Secretary of Defense James Schlesinger, who took similar measures to constrain an increasingly erratic Richard Nixon in 1974.

Both incidents also highlight a longstanding but largely unresolved danger: the lack of guardrails to prevent a reckless or unstable president from starting a nuclear war.