A top Pentagon official is stepping down at the end of the month, deepening the gap in confirmed leaders within the Defense Department’s policy shop as Sen. Tommy Tuberville continues his blockade of senior military and civilian nominations.

Mara Karlin, best known for her role in developing the Biden administration’s National Defense Strategy, is leaving government for a teaching role at the end of the year, according to Sasha Baker, the acting undersecretary of defense for policy.