On Monday, Ambassador Tina Kaidanow, who was a longstanding employee of the State Department before transitioning into her new role as senior adviser for international cooperation with the Defense Department, announced her resignation. Michael Vaccaro, the Pentagon’s Director for International Armaments Cooperation, will step in and fill the role until a replacement can be identified. Kaidanow’s departure alone may not have been enough to garner much attention from the press, but her’s is only the latest in what some are calling an “exodus” of Pentagon officials — as five have now announced their intent to leave in just the past week.

“The department remains committed to the development and implementation of international cooperative programs and defense exportability efforts to foster cooperation with U.S. allies on research, development, production and support of weapons systems and related equipment,” Lt. Col. Michael Andrews said in a statement. “The department will not provide anything further on this personnel matter.”

Prior to Kaidanow’s announcement, four other officials notified the Defense Department of their intent to leave their positions this week. Those departures include Randal Schriver, the Pentagon’s senior Asia policy official; Jimmy Stewart, who has been serving as the acting Undersecretary of Defense for Personnel and Readiness since October 2018; Steven Walker, the head of the Pentagon’s secretive Defense Advanced Research Projects Agency (DARPA); and Kari Bingen, principal Deputy Undersecretary of Defense for Intelligence.

These departures highlight an ongoing issue within the Pentagon, as departures are often filled with “acting” replacements, leading to concerns about the stability of leadership within the upper echelons of America’s defense infrastructure. Even Defense Secretary Mark Esper, who stepped in after Patrick Shanahan filled the role in an “acting” capacity for nearly a year and a half, acknowledged the lacking stability among the military’s civilian leadership in August. He expects billets that have been standing vacant for some time to soon be filled.