Murphy argues that the bill is merely a “restatement of existing law”—specifically the War Powers Act of 1973—applied to the pressing case of North Korea, though he allowed that the president likely has a different interpretation of his authorities under Article II of the Constitution. (The War Powers Act establishes procedures for when the president should consult with Congress before committing U.S. forces to an armed conflict.) “By making it clear what Congress’s interpretation is of the president’s war-making ability in North Korea, I think we begin to bind his hands,” he told me.

“I think we’re fools if we don’t start taking the president at his word,” said Murphy, who sits on the Senate Foreign Relations Committee and has been a leading Democratic voice on foreign policy since Trump’s election. “He has shown an enthusiasm for military force against North Korea in his Twitter account that is extraordinary.”

According to Murphy, it’s misguided to dismiss Trump’s belligerence as bluster or a negotiating tactic, or to believe that the experienced generals advising the president will restrain Trump from launching a potentially catastrophic preventive war against North Korea.

“Increasingly, President Trump does what he says, even against the advice of his advisers,” Murphy noted. “His advisers told him not to decertify the Iran [nuclear] agreement, and he did it. His advisers told him not to stop paying the insurance companies, and he did it. Maybe his advisers are telling him not to launch a preemptive strike against North Korea, but what about his history gives us confidence that he wouldn’t do that too?” (As Trump recently told reporters, “I feel stronger and tougher on [North Korea] than other people. … I listen to everybody, but ultimately my attitude is the one that matters, isn’t it? That’s the way it works.”)

“My increased worry comes not just from Trump’s rhetoric, but also from a changed tone that some of us are hearing from military leadership,” Murphy continued. “It’s not as if someone is coming up to the Hill and sharing invasion plans with us, but it just strikes me that the military is at a different level of readiness and preparation today than they were even a few months ago.”

Murphy rejected the notion, suggested by National-Security Adviser H.R. McMaster and other administration officials, that the United States would be confronted with an imminent threat if North Korea obtains the capability to reach the American mainland with a nuclear-tipped long-range missile (a milestone that the North could reach in a matter of months, according to CIA Director Mike Pompeo). He didn’t go into detail about what he would view as an imminent threat from North Korea, but he told me that “it clearly would require the administration to show something beyond the mere possession of a weapon that could hit the United States in order to clear the bar.”