Two days after the 2016 presidential election, I held a town hall at the United States Mission to the United Nations. American diplomats were in shock; the president-elect had pledged to undo much of what we had helped achieve internationally.

One of the first people who got up to speak, a Foreign Service officer, said: “I don’t agree with a lot of the things Trump has said. But he doesn’t seem to have a lot of people experienced in foreign policy in his inner circle. He and his team will need us. And we will have the same duty to our country — and the same privilege of serving our country — on Jan. 20, as we had when we served George W. Bush and Barack Obama.” This sentiment was echoed by speaker after speaker.

Many of them, along with some of our most capable diplomats, have since left government. Ridiculed as “Obama holdovers” and unable to defend policies that depart so markedly from American interests, our diplomatic corps has been hollowed out. If Mike Pompeo, the director of the C.I.A., wins confirmation as Rex Tillerson’s replacement as secretary of state, fixing this would become his responsibility. He can’t change the president, but he can make it his mission to revitalize America’s diplomatic corps and get back to trying to solve problems in the real world.

Mr. Pompeo should start by putting forward nominations for dozens of open foreign ambassadorships (including key posts like Egypt, Jordan, South Korea, Turkey and South Africa). This would give us the means of engaging officials in those countries — to promote investment, protect Americans abroad and combat terrorism. It would also send a signal that diplomats matter.