WASHINGTON — Former Secretary of State Rex W. Tillerson once admitted that he had never known a single American diplomat before joining the Trump administration, a surprising admission for a well-traveled executive that many in Foggy Bottom found insulting and dispiriting.

By contrast, his successor, Mike Pompeo, assured hundreds of diplomats on Tuesday that he not only knew many of them already, but that he also had a deep appreciation for their work and commitment to the United States.

“You chose to be a foreign service officer, or a civil servant, or to come work here in many other capacities — and to do so because you’re patriots, and great Americans, and because you want to be an important part of America’s face to the world,” Mr. Pompeo said in brief remarks during a formal arrival ceremony at the department’s headquarters.

“My mission will be to lead you and allow you to do that, the very thing you came here to do,” he said, to great applause. Mr. Pompeo also promised the crowd that he would help American diplomats regain their “swagger,” alluding to a department that had been diminished under Mr. Tillerson.