Office of the Assistant Secretary of Defense for Nuclear, Chemical, and Biological Defense Programs

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The Office of the Assistant Secretary of Defense for Nuclear, Chemical, and Biological Defense Programs (OASD(NCB)) leads DoD efforts to ensure a safe, secure, and effective U.S. nuclear deterrent against weapons of mass destruction threats. As the world returns to Great Power competition and the recognition that threats against the United States, its allies and interests are both proliferating and becoming more difficult to challenge, the OASD(NCB) is at the forefront of U.S. efforts to sustain and modernize the nuclear deterrent, while simultaneously providing chemical and biological defense and compliance with international NCB treaties and agreements. From the operational, to the administrative, to the speed of response and production, the OASD(NCB) is reshaping the way the DoD meets and responds to WMD threats.

Our Vision, Mission, and Values

Vision: Lead DoD efforts in preparing for, deterring, and mitigating current and future weapons of mass destruction (WMD) threats.

Mission: Sustain and modernize the U.S. nuclear deterrent; develop capabilities to detect, protect against and respond to WMD threats; ensure DoD compliance with nuclear, chemical, and biological treaties and agreements; continue to work with allies and partners to strengthen our collective countering weapons of mass destruction (CWMD) capabilities; and advance the United States nonproliferation goals.

Values: Commitment to the Mission People First Teamwork Growth Mindset Integrity Inclusiveness

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Strategic Goals

Secure, sustain, and maintain the U.S. nuclear deterrent and recapitalize the nuclear enterprise.

Enable Joint Force freedom of maneuver in chemical, biological, radiological, and nuclear (CBRN) environments.

Develop capabilities to counter CBRN threats and respond to and manage the consequences of WMD effects.

Support and enable allies and partners to enhance deterrence and counter WMD proliferation while complying with relevant international treaties and agreements.

Streamline policies, procedures, and guidelines to promote efficiency, effectiveness, transparency and coordinate intra- and interagency efforts.


Dr. Brandi C. Vann, PhD
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Dr. Brandi C. Vann, PhD

Performing the Duties of Assistant Secretary of Defense for Nuclear, Chemical, and Biological Defense Programs (ASD(NCB)) and Principal Deputy Assistant Secretary of Defense for Nuclear, Chemical, and Biological Defense Programs


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Ms. Rebecca K.C. Hersman

Ms. Rebecca K.C. Hersman

Director, Defense Threat Reduction Agency (DTRA)

Drew Walter

Drew Walter

Deputy Assistant Secretary of Defense for Nuclear Matters (DASD(NM))

Kingston A. Reif

Kingston A. Reif

Deputy Assistant Secretary of Defense for Threat Reduction and Arms Control (DASD(TRAC))

Ian Watson

Ian Watson

Deputy Assistant Secretary of Defense for Chemical and Biological Defense (DASD(CBD))


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Nuclear Deterrent


Ensure the safety, security and effectiveness of the U.S. nuclear deterrent.

Countering WMD


Prevent the spread of, protect against, and respond to weapons of mass destruction threats.

Countering Improvised Threats


Providing expertise to detect, deter, and defeat WMD and emerging threats.

Treaties and Agreements


Ensure DoD compliance with nuclear, chemical and biological treaties and agreements.



Nuclear Matters serves as the focal point for DoD activities and initiatives related to the dual missions of sustaining a safe, secure, and effective nuclear deterrent and countering the threat from nuclear terrorism and nuclear proliferation. In this capacity, the ODASD(NM) also serves as a primary point of contact for Congress, the interagency, and the public. The ODASD(NM) also provides staff support to the Nuclear Weapons Council and the Security and Incidence Response Council as well as their subordinate committees. The office is comprised of representatives from all areas of the nuclear community, to include the U.S. Navy, the U.S. Air Force, the Department of Energy via the National Nuclear Security Agency, Los Alamos National Laboratory, Lawrence Livermore National Laboratory, Sandia National Laboratories, the Kansas City National Security Campus, and the Federal Bureau of Investigation.

Visit the Nuclear Matters website.


Chemical and Biological Defense coordinates and resources the delivery of Chemical, Biological, and Radiological (CBR) defense capabilities to protect national interests at home and abroad. The ODASD(CBD) ensures the integration of DoD efforts related to requirements development, science & technology, advanced development, test and evaluation, and procurement to support the Joint Services priorities and coordinates the delivery of those CBR defensive capabilities through the CBD Program Objective Memorandum (POM).

The office also coordinates and integrates the development and delivery of CBR defensive capabilities with the broader countering weapons of mass destruction (WMD) responsibilities to enable the prevent of WMD or transfer. The ODASD(CBD) serves as a focal point to ensure DoD support for homeland defense and overseas contingency operations against existing and emerging CBRN threats.

Visit the Chemical and Biological Defense website.


The Deputy Assistant Secretary of Defense for Threat Reduction and Arms Control is the principal advisor to the ASD(NCB) for acquisition oversight, implementation, and compliance with nuclear, biological, and chemical treaties; cooperative threat reduction; chemical demilitarization programs; and building global partner capacity to counter weapons of mass destruction. The ODASD(TRAC) exercises oversight of the Defense Threat Reduction Agency-executed Cooperative Threat Reduction Program and provides oversight of the Chemical Demilitarization Program. Additionally, the ODASD(TRAC) provides oversight of implementation and compliance with existing and prospective nuclear, biological, and chemical arms control agreements in accordance with DoDD 2060.1, Implementation of, and Compliance with, Arms Control Agreements; integrates combating weapons of mass destruction programs; and assists the ASD(NCB) as Executive Secretary of the Counterproliferation Program Review Committee (CPRC) and Chair of the Standing Committee of the CPRC.

Visit the Threat Reduction and Arms Control website.


The Defense Threat Reduction Agency (DTRA) is the only Department of Defense organization focused exclusively on countering and deterring weapons of mass destruction (WMD) and emerging threats. Designated both a Defense Agency and Combat Support Agency, DTRA identifies, develops, and fields leading-edge solutions that provide the Military Services, Combatant Commands, U.S. Interagency, and foreign partners/allies unparalleled capabilities to detect, deter, and defeat WMD and emerging threats. DTRA's unique technical expertise across the chemical, biological, radiological, nuclear, and emerging threat space, enables nonproliferation, counterproliferation, interdiction, arms control, and risk-reduction missions worldwide. From the gray zone through great power competition, DTRA works with our mission partners to preserve peace and prepare for uncertainty by delivering innovative capabilities, objective analysis, and world-class subject matter expertise.

Visit the Defense Threat Reduction Agency website.


The Atomic Energy Act of 1946 established the civilian Atomic Energy Commission (AEC) to replace the Manhattan Project. The Atomic Energy Act of 1954 established the DoD Military Liaison Committee (MLC) to coordinate military requirements with the AEC. The MLC functioned as the authorized channel of communication between the Department of Defense (DoD) and the Department of Energy (DOE) on all atomic energy matters relating to the military applications of atomic weapons or atomic energy. The committee addressed matters of policy, programming, and commitment of funds to the military application of atomic energy.

In 1951, the Secretary of Defense moved the MLC to the Pentagon and designated its chairman as the Deputy to the Secretary of Defense for Atomic Energy Matters. In 1953, this position was re-designated under DoD Directive 5130.2 as the Assistant to the Secretary of Defense for Atomic Energy (ATSD(AE)).

From 1982-1996, the role of the ATSD(AE) expanded to include issues associated with chemical and biological weapons, the implementation of arms control treaties and agreements, counterproliferation programs, and the coordination of the Cooperative Threat Reduction (CTR) Program, which assists in the elimination of weapons of mass destruction (WMD) in the former Soviet states. Additionally, in 1994, the Defense Nuclear Agency (DNA) was placed under the oversight of the ATSD(AE). DNA is now known as the Defense Threat Reduction Agency (DTRA).

As part of the 1996 Defense Authorization Act, the ATSD(AE) became the Assistant to the Secretary of Defense for Nuclear and Chemical and Biological Defense Programs (ATSD(NCB)), reflecting the expanded mission of the organization and more accurately describing its multiple functions.

Between 1997 and 2001, the Administration declined to nominate anyone to serve as the ATSD(NCB), having determined, as part of the Defense Reform Initiative, that the position should be eliminated. Congress, however, maintained that the position was necessary to ensure appropriate senior-level policy oversight and implementation guidance within the Department.

While the ATSD(NCB) position was vacant, the Under Secretary of Defense for Acquisition, Technology, and Logistics (USD(AT&L)) assumed the responsibilities of the ATSD(NCB). The USD(AT&L) delegated many of the ATSD(NCB) nuclear weapons-related duties to the Director of Defense Research and Engineering (DDR&E) until November 2001, when the ATSD(NCB) position was again filled.

In 2001, the ATSD(NCB) position was filled by the Senate-confirmed appointment of Dr. Dale Klein. The Honorable Dale Klein held the ATSD(NCB) position until June 30, 2006, when he left to become the Chairman of the Nuclear Regulatory Commission. From June 2006 until August 2008, Dr. Arthur T. Hopkins served as the acting ATSD(NCB). In August 2008, The Honorable Mr. Fred Celec was sworn in as the ATSD(NCB). On May 18, 2009, the Honorable Andrew C. Weber was confirmed as the ATSD(NCB). In January 2011, Congress redesignated the ATSD position as the Assistant Secretary of Defense for Nuclear, Chemical, and Biological Defense Programs (ASD(NCB)). Mr. Weber served as the ASD(NCB) through October 17, 2014. Dr. Hopkins served again as Acting ASD(NCB) from October 18, 2014 through November 30, 2017. The Honorable Guy B. Roberts served as the ASD(NCB) from November 20, 2017 through April 4, 2019. The Honorable Alan R. Shaffer performed the duties of the ASD(NCB) until January 2021. Dr. Brandi C. Vann served as the Acting ASD(NCB) until Ms. Deborah Rosenblum was sworn in as the ASD(NCB) in August 2021.


DoDD 5134.08, Assistant Secretary of Defense for Nuclear, Chemical, and Biological Defense Programs (ASD(NCB))

DoDD 5105.62, Defense Threat Reduction Agency (DTRA)

Title 50 US Code, Chapter 40, Defense Against Weapons of Mass Destruction

Title 50 US Code, Chapter 43, Preventing Weapons of Mass Destruction Proliferation and Terrorism

Title 10 US Code, section 179, Nuclear Weapons Council

2023 Biodefense Posture Review

2022 National Defense Strategy (including 2022 Nuclear Posture Review and 2022 Missile Defense Review)

2022 Nuclear Posture Review (NPR) Fact Sheet

2022 National Biodefense Strategy and Implementation Plan

2018 National Biodefense Strategy

2018 National Strategy for Countering Weapons of Mass Destruction Terrorism

2017 National Security Strategy

2014 Quadrennial Defense Review

National Strategy for Countering Biological Threats