Eric Chewning, chief of staff to Defense Secretary Mark Esper, will step down at the end of the month to take a job in the private sector. His departure—the reason for which has not been specified—comes after several senior officials left the Pentagon last month or announced they were stepping down. He will be replaced by Jen Stewart, the top Republican staffer on the House Armed Services Committee and a former top adviser to the chairman of the Joint Chiefs, Pentagon spokeswoman Alyssa Farah said in a statement. Esper said in a statement that Stewart has “deep expertise on national security issues,” which will be crucial in the Pentagon’s fight against the growing threats posed by Russia and China. Chewning, who previously served as an Army intelligence officer and combat veteran, has worked under four Pentagon chiefs and has been responsible for leading Esper’s executive staff and advising him on issues concerning the Defense Department. 

He joined the Pentagon in 2017 as deputy assistant secretary and replaced Jim Mattis as the chief of staff in January 2019. “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 on Monday. “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.”