Staff turnover in the Trump administration has been extraordinary, but some staff departures are more notable than others. More to the point, it’s worth paying attention not just to who leaves their positions, but why and how they part ways with the administration.

Chuck Park was, up until yesterday, a U.S. Foreign Service official who’d served under different presidents from different parties. The child of immigrants, Park was inspired by the idea of American exceptionalism, and he “felt a duty to the society that welcomed my parents and allowed me and my siblings to thrive.”

He proceeded to serve tours abroad, working to spread “what I believed were American values: freedom, fairness and tolerance.”

Yesterday, Park resigned and wrote an op-ed for the Washington Post explaining why.

Ask to read the commission of any Foreign Service officer, and you’ll see that we are hired to serve “during the pleasure of the President of the United States.” That means we must serve this very partisan president. Or else we should quit. I’m ashamed of how long it took me to make this decision. My excuse might be disappointing, if familiar to many of my colleagues: I let career perks silence my conscience. I let free housing, the countdown to a pension and the prestige of representing a powerful nation overseas distract me from ideals that once seemed so clear to me. I can’t do that anymore. My son, born in El Paso on the American side of that same Rio Grande where the bodies of Óscar Alberto Martínez Ramírez and his daughter were discovered, in the same city where 22 people were just killed by a gunman whose purported “manifesto” echoed the inflammatory language of our president, turned 7 this month. I can no longer justify to him, or to myself, my complicity in the actions of this administration. That’s why I choose to resign.

It’s a striking perspective in its own right, but reading Park’s op-ed, I was reminded of how increasingly common it’s become to hear from diplomatic officials like him who haven’t just resigned, but who’ve also taken care to explain their reasoning to the public.

Last fall, for example, Roberta Jacobson, who’d stepped down as the U.S. ambassador to Mexico, wrote an interesting op-ed for the New York Times explaining, in reference to the Trump White House’s agenda, “I cannot pretend anything less than relief at no longer having to defend the indefensible.”

Around the same time, James Melville, another U.S. diplomat with more than three decades of experience, resigned as U.S. ambassador to Estonia. In an op-ed for the Washington Post, the career diplomat argued in support of a foreign policy vision that’s largely the opposite of the current president’s vision: rules-based order, skepticism toward Russia, and support for the United States’ longtime allies.

“Arrogance does not suit us well,” Melville wrote. “ ’America First’ is a sham.”

In March 2018, John Feeley stepped down as the U.S. ambassador to Panama, and soon after wrote in a Washington Post op-ed, “I resigned because the traditional core values of the United States, as manifested in the president’s National Security Strategy and his foreign policies, have been warped and betrayed. I could no longer represent him personally and remain faithful to my beliefs about what makes America truly great.”

Don’t be surprised if this list grows.