Lonnie Bunch, the secretary of the Smithsonian Institution, was already slipping into the past tense when we walked together through the National Museum of American History in February.Occasionally, as we stood before an exhibit, he’d discuss his role leading the largest museum system in the world as though he had already stepped away. Even then, there wasn’t a question of if he would retire soon, but how soon. He spoke longingly of a future life in which he took fewer flights, slept in fewer hotels, spent more time with his grandchildren. He desperately wanted more time to write. He told me he still has more books in him. Now he will get the time.Bunch announced on Tuesday that he will retire at the end of the year. “I am extraordinarily proud of what we have accomplished together,” he wrote in a statement. “I leave with pride and sadness, gratitude and joy, and with enormous confidence in the people who will carry this remarkable institution forward.”Bunch said that pressure from the Trump administration played no role in his decision. That may well be true, but Donald Trump’s second term has played a disproportionate role in shaping Bunch’s final few years in charge. The 18 months that Bunch spent holding off the White House’s efforts to influence the Smithsonian reinvigorated his commitment to the institution. But it seemed to me that he was exhausted. He did not seem to relish writing memos assuring his staff and the broader public (while reminding the president) that the Smithsonian was nonpartisan and singularly guided by scholarship; he did not want to go to work under the constant threat of the federal government pulling funding; he did not want to have lunch with the president while waiting for “the sword of Damocles to come take my head off,” as he admitted during a talk at UCLA last year.He did so because that was what the moment required. He did so because he loves the Smithsonian, which has been part of his life since he first began a job at the National Air and Space Museum nearly half a century ago. But this, I thought, was not how the secretary of the Smithsonian should have to be spending his time. It all seemed like a massive distraction from the mission. I could not help but think of Toni Morrison’s observation during a 1975 keynote address at Portland State University about “the function, the very serious function of racism, which is distraction. It keeps you from doing your work. It keeps you explaining, over and over again, your reason for being.”Over and over again, Bunch was in a position of having to explain the Smithsonian’s reason for being: “At the Smithsonian, our work is driven by scholarship, accuracy and an uncompromising commitment to tell the fullness of America’s story,” he wrote to employees in response to this summer’s White House report, which accused the National Museum of American History of ideological bias. “As public servants and the keepers of this institution, we are charged with helping a nation find understanding, hope and clarity and as part of that duty, we are dedicated to excellence, reflection and growth.”Perhaps Bunch, ever the diplomat, would disagree that Trump’s social-media posts lamenting that the Smithsonian spends too much time talking about slavery distracted anyone from the mission. (Ditto Trump’s plan to place signs on the National Mall accusing a museum of being anti-American.) And although I know from speaking with multiple staffers that Trump’s attacks on the institution bolstered their commitment, time spent defending one’s work is time away from actually doing that work.[Read: Trump’s trigger warnings]Last year, when the administration first put out an executive order targeting the Smithsonian, people flocked to the Smithsonian museums, particularly the National Museum of African American History and Culture, of which Bunch was the founding director. Many people had watched what was being done to the Kennedy Center, and it seemed like the Smithsonian might be the next Washington institution to experience a Trump-world takeover.This summer has been a reminder for me of the singular role the Smithsonian plays in American life. I live in suburban Maryland, right outside of Washington, D.C., and this summer, our guest room has been occupied by a merry-go-round of guests visiting the District. Almost all of them have made sure that they got to the National Mall to explore the museums. It could be my little cousins marveling at the planes hanging overhead at the National Air and Space Museum; my friend from graduate school spending the entire day at the National Museum of African American History and Culture and feeling like there was still so much to see; my own children going to the National Zoo with their grandparents to see the giant pandas. The Smithsonian is a sprawling organization that represents the expansiveness (as well as the complexity and contradictions) of the world and the country we live in. Despite the diatribes from the administration, people yearn for that enormity and messiness. They don’t run from it.Months ago, when I spoke with the Yale historian David Blight, a longtime friend of Bunch, he told me that when Bunch left his post, he would have the opportunity to speak powerfully and personally about the moment we are in. “He could have a moment to really say something about the terrible consequences of these history wars,” he said. “And there’s really almost nobody that quite has his pulpit when he chooses to use it.”Bunch has already alluded to the fact that he won’t go quietly—that he might have more to say when he is no longer constrained by his responsibilities to the institution.Whoever succeeds him won’t have an easy task. Few historians are as respected—both within the field and by the general public—as Bunch. In the hours since he announced his retirement, I’ve received calls and messages mourning his departure, as if a beloved head of state had stepped down early. There is also a similar sense of concern. Will Bunch’s departure accelerate the White House’s attacks on the Smithsonian or quiet them? Does anyone else have the skill set to defend the museums in the way he has? Whatever is needed to lead an entity that’s caught the eye of a heavy-handed president, Bunch’s recent experience shows that the next Smithsonian secretary will need to make at least one significant sacrifice: their time.