Secretary of State Mike Pompeo has tapped Carnegie Mellon University Professor Kiron Skinner, a nationally known author and Hoover Institution research fellow, as the State Department’s top planner.

Ms. Skinner, who has worked with former Secretaries of State Condoleezza Rice and George Shultz, represents what Mr. Pompeo said is a major personnel addition as he moves to fulfill promises to rebuild department staffing.

Mr. Pompeo described Ms. Skinner as “a national security powerhouse” and “a one-woman, strategic thinking tour de force” in a statement to The Wall Street Journal. “I’m confident that she will enhance our influence overseas, protect the American people, and promote our prosperity,” he said.

Foreign policy experts and former holders of the post said Ms. Skinner’s impact will depend on how Mr. Pompeo structures the job, and whether the administration is open to her ideas. “The real question is how will the new director’s role be defined?” said longtime diplomat Dennis Ross, who held the post during the George H.W. Bush administration.

As director of the Policy Planning Staff, Ms. Skinner will be responsible for providing strategic guidance and helping ensure that the day-to-day efforts of the department serve the overall strategy. Ms. Skinner will start on Sept. 4, succeeding Brian Hook, who now heads the State Department’s Iran Action Group.