Eric Fanning will become the next acting undersecretary of the Army, Defense Secretary Ash Carter announced July 2. Rosenbach will replace Fanning as Carter’s chief of staff. Fanning previously served as deputy Navy secretary, Air Force undersecretary, and deputy director of the Commission on the Prevention of Weapons of Mass Destruction Proliferation and Terrorism. Rosenbach, who moves into his new job, now is serving as Carter’s deputy chief of staff. He previously served as assistant secretary of defense for homeland defense and global security.