Deputy Assistant Secretary of Defense Eric Chewning discusses the importance of securing a supply base, especially in an era of cyberthreats.

WASHINGTON — Eric Chewning, who has served as chief of staff for both acting Secretary of Defense Pat Shanahan and current Secretary of Defense Mark Esper, will be exiting the Defense Department at the end of the month to return to the private sector.

He will be replaced by Jen Stewart, currently the minority staff director for the House Armed Services Committee.

“I’m grateful for Eric’s professionalism, judgment, and leadership over the last seven months as I moved into the Secretary of Defense role,” Esper said in a statement provided to Defense News. “In an incredibly demanding job, Eric has been a source of calm and tireless work. We wish him all the best upon his return to the private sector.”

Despite a job at Morgan Stanley, Chewning left the private sector to enlist in the Army following the 9/11 attacks; he later was commissioned as an Army intelligence officer. Afterward, he returned to the private sector, and before joining the Pentagon was a partner at McKinsey & Company.

Chewning entered the Defense Department in October 2017 as the head of the Pentagon’s industrial base office, where he helped oversee a major White House-ordered review of the defense-industrial base. Last January, he was tapped by then-acting Defense Secretary Shanahan as his chief of staff, and was kept on in that role when Esper took over in August.

Chewning’s replacement, Stewart, previously served as a senior adviser to Gen. Joseph Dunford, a former chairman of the Joint Chiefs of Staff. Stewart also served as the national security adviser to Speakers of the House Paul Ryan and John Boehner.

“I have known Jen for years and I’m excited to bring her into the Department,” Esper said. “Her deep expertise on national security issues will be a great addition to our team as we continue implementing the National Defense Strategy.”

In a statement, Dunford praised Chewning’s “extraordinary leadership within the Department during a challenging period" that saw significant turnover inside the department, including the handover from Shanahan to Esper.

“On a personal level, I appreciated his character, integrity, and engaged leadership. I was very proud to work alongside Eric and to call him a friend,” Dunford said. “Eric leaves big shoes to fill but Secretary Esper couldn’t have selected a more qualified or suitable candidate. I have known Jen Stewart for years. She has earned a reputation as a knowledgeable, competent, and extremely hard working strategic leader. She was among my most trusted advisors and confidantes during my first two years as the 19th Chairman. The Secretary, the Department, and the Nation will be well served with Jen as the Chief of Staff.”

Chewning becomes the sixth high-profile exit from the Pentagon in the last month, although there should be no gap between his exit and Stewart’s start. Pentagon spokeswoman Alyssa Farah said the building “continues to bring in high quality personnel" to fill the empty spots in the building.

“This week three new Senate-confirmed appointees will be sworn in, while three nominees await Senate action, and additional nominations are expected in coming weeks,” Farah said. “Also this week, four new senior [Senior Executive Service] appointees will be sworn in, joining approximately a dozen senior SES leaders brought into the Department in the last few months of 2019.”