One afternoon in late September, I sat down with Rex Tillerson on what, in hindsight, may well have been his last comparatively normal day as secretary of state. It was a little more than 72 hours before President Donald Trump would take to Twitter to declare that Tillerson, his top diplomat, was “wasting his time trying to negotiate with Little Rocket Man,” as the president now refers to the North Korean leader, Kim Jong-un, and admonish Tillerson: “Save your energy Rex, we’ll do what has to be done!” Which was a few days before NBC News would report that Tillerson, after a July meeting with Trump, called the president a “moron” and wanted to resign until Vice President Mike Pence talked him out of it. Which was just a couple hours before Tillerson would hold an extraordinary news conference in the State Department’s Treaty Room — the magisterial, blue-walled chamber where secretaries of state typically greet foreign dignitaries — in order to tell reporters that Trump “is smart”; deny that he ever considered resigning; and refuse to answer a question about whether he had indeed called the president a moron.

But even before all that, sitting in a silk-upholstered chair in front of a fireplace in his office, his State Department-seal cuff links peeking out from the sleeves of his navy blue suit, the impossibility of Tillerson’s assignment was apparent. He was about to embark on his third trip to Asia as secretary of state, part of his efforts to bring about a peaceful resolution to the North Korean nuclear crisis, so I asked him if Trump’s tweets on the topic — threatening in August that “military solutions are now fully in place, locked and loaded,” and in September that if the United States “is forced to defend itself or its allies, we will have no choice but to totally destroy #NoKo” — were in any way helpful to what he was trying to accomplish.

Tillerson let out a short sigh. “Look, on the president’s tweets,” he said, “I take what the president tweets out as his form of communicating, and I build it into my strategies and my tactics. How can I use that? How do I want to use that? And in a dynamic situation, like we deal with here all the time — and you can go walk around the world, they’re all dynamic — things happen. You wake up the next morning, something’s happened. I wake up the next morning, the president’s got a tweet out there. So I think about, O.K., that’s a new condition. How do I want to use that?” Tillerson continued: “Our strategies and the tactics we’re using to advance the policies have to be resilient enough to accommodate unknowns, O.K.? So if you want to put that in an unknown category, you can. It certainly kind of comes out that even I would say, ‘I wasn’t expecting that.’ But it doesn’t mean our strategies are not resilient enough to accommodate it.”

Accommodating the president, rather than working with him, is not a normal mission for a secretary of state — and for Tillerson, it seems to be an increasingly doomed one. “The president’s always saying, ‘Rex’s not tough,’ and ‘I didn’t know he was so establishment,’ ” says one Trump adviser. After Tillerson’s “moron” gibe became public, the president, while dismissing the report as “fake news, ” also told Forbes, “if he did that, I guess we’ll have to compare I.Q. tests. And I can tell you who is going to win.” The question among many people inside and outside the Trump administration is not necessarily what’s keeping Tillerson from resigning; it’s what’s stopping Trump from firing him. One Trump-administration official offered me a tentative theory: “Losing a chief of staff in the first year is a big deal, but losing a secretary of state is an even bigger one.”