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Rebecca Zimmerman

Performing the Duties of Assistant Secretary of Defense for Homeland Defense and Hemispheric Affairs


Rebecca Zimmerman is Performing the Duties of the Assistant Secretary of defense for Homeland Defense and Hemispheric Affairs. She is also the Acting Principal Deputy Assistant Secretary of Defense for Homeland Defense and Hemispheric Affairs.

Ms. Zimmerman previously served as the Deputy Assistant Secretary of Defense for Homeland Defense Integration and Defense Support of Civil Authorities. In this role, Ms. Zimmerman is responsible for the development of homeland defense, defense support of civil authorities, and chemical, biological and nuclear preparedness policy, including overseeing the implementation of policy, plans, and programs that address the emerging security challenges faced by the nation. Working closely with Federal, State, and local leadership, law enforcement, public health, and emergency management, she oversees DoD’s response to national emergencies in support of lead federal agencies.

Prior to her appointment, Ms. Zimmerman served as Deputy Assistant Secretary of Defense for Afghanistan, Pakistan, and Central Asia since February 16, 2021. Ms. Zimmerman spent two decades as a researcher and policy advisor, including at the RAND Corporation, as Editor-in-Chief of War on the Rocks, and in the private sector. Over the course of her career, Ms. Zimmerman has been seconded to multiple deployed operational commands, served on several study task forces reporting to the Chairman of the Joint Chiefs of Staff, and as RAND’s liaison to Army Operations. She is an author of numerous studies, including on U.S. military inter-service competition, organizational aspects of competition with China and Russia, soldier attitudes and attrition, and Afghanistan policy.

Ms. Zimmerman holds a B.A. in international relations with honors from Stanford University and an M.A. in strategic studies from the Johns Hopkins University, School of Advanced International Studies.