Joe Kasper leaves the role voluntarily, but his departure adds to the sense of instability that has gripped the Defense Department for weeks.

Joe Kasper, Hegseth’s chief of staff, is the fourth top official to be ousted in the last week amid turmoil at the Pentagon.

Defense Secretary Pete Hegseth's chief of staff, Joe Kasper, stepped down Thursday. With his departure and the firing of three top Hegseth aides over leak accusations they deny, Hegseth's "circle of top advisers" has "shrunk in recent days to little more than his wife,