Nuclear Bunker-Busters and Article VI of the Non-Proliferation Treaty

Andrew J. Grotto
February 05, 2005
The Bush administration's proposed budget for FY 2006 contains appropriation lines for resuming research on the nuclear bunker-buster. This proposal is likely to renew the heated debate within the United States over the role and shape of U.S. nuclear forces. It also raises an important legal issue: does this research cause the United States to run afoul of its disarmament obligations under Article VI of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT)?
With the first post-9/11 NPT Review Conference set to take place in May 2005, the timing of this development is especially sensitive. At the conference, the United States is expected to press for tougher global rules on the spread of nuclear weapons and the fuel-cycle technology needed to produce weapons-usable fissile materials, in light of North Korea's withdrawal from the NPT and its assertion that it has nuclear weapons; the questionable nuclear activities undertaken by Iran; and the threat of terrorist acquisition of nuclear weapons.
Non-nuclear weapon states, in turn, are expected to link any agreement on tougher rules to stronger steps by the nuclear-weapon states towards nuclear disarmament, as required, in their view, by Article VI of the NPT and other obligations undertaken by the nuclear-weapon states to reduce and/or eliminate their nuclear arsenals. This Insight identifies the principle lines of argument used by defenders and critics of the Article VI legality of the nuclear bunker-buster research.
The research in question would consider the technical feasibility of modifying existing high-yield nuclear warheads to burrow deep into the ground before exploding. Such a hypothetical nuclear "bunker-buster"--also known by its technical name, Robust Near-Earth Penetrator (RNEP)--would be designed to destroy enemy command and control facilities, safely neutralize buried stockpiles of chemical or biological weapons and the laboratories that produce them, and dissuade states from pursuing weapons of mass destruction in the first place. Future generations of the weapon could have a low yield in order to minimize collateral damage, including radioactive fallout from the blast. Unlike strategic nuclear weapons, which are designed to deter attacks, these innovations would be designed to make the nuclear bunker-buster more "usable" in actual combat operations.[1]
Though the nuclear bunker-buster is intensely controversial among nuclear weapons and nonproliferation experts in the United States, research and development of new nuclear weapons is not a recent phenomenon. Throughout the NPT's history and as recently as several years ago, the United States (along with other nuclear-weapons states) has added new nuclear weapons designs to its arsenal of operational forces.[2] The U.S. last carried out a nuclear test--often a necessary step to verify the reliability of a new nuclear weapon--in 1992, and has observed a self-imposed moratorium on nuclear testing ever since.
In 1993, Congress enacted the Spratt-Furse Amendment, which prohibited research that could lead to low-yield nuclear weapons, such as low-yield bunker-busters. In May 2003, however, Congress repealed the amendment. The administrator of the National Nuclear Security Administration--the agency within the Department of Energy responsible for researching, developing, and maintaining the United States' nuclear arsenal--promptly encouraged U.S. weapons laboratories to "take advantage of this opportunity."[3] Congress approved funding specifically for research into the RNEP for FY 2003 and FY 2004.
Funding for this research ran into trouble in late 2004, however. Citing concerns that the research "send[s] the wrong signal to the rest of the world" about the utility of nuclear weapons and America's commitment to nuclear nonproliferation, Congressman David L. Hobson (R-OH) led the charge in Congress to eliminate funding for the program for FY 2005.[4]
If Congress approves the administration's FY 2006 budget request, the research will resume once again, reviving concerns about whether the United States is living up to its nuclear disarmament obligations centering on Article VI of the NPT. Though this would not be the first instance that the United States and other nuclear-weapon states have been accused of not adequately fulfilling their legal obligations under Article VI,[5] the timing now is especially sensitive due to the NPT Review Conference set to take place in May 2005, where nuclear-weapons states' compliance with Article VI is likely to be an issue.
NPT Article VI
The core legal issue concerns what restrictions, if any, Article VI of the NPT, and possibly subsequent commitments agreed to by the states parties to the NPT, place on the research and development of new nuclear weapons.
Article VI reads:
Each of the Parties to the Treaty undertakes to pursue negotiations in good faith on effective measures relating to cessation of the nuclear arms race at an early date and to nuclear disarmament, and on a Treaty on general and complete disarmament under strict and effective international control.
There are three distinct classes of obligation in this text on the theme of disarmament: the nuclear arms race, nuclear disarmament, and military disarmament more broadly. The former two are pertinent to the present discussion.
Proponents of the NPT legality of nuclear bunker-buster research point out that nothing in the text of Article VI or its negotiating history explicitly prohibits such research, and that each of the nuclear-weapons states has at various times during the treaty's history developed and deployed new nuclear weapons.[6] In their view, this implies that there is nothing illegal per se about researching and developing a nuclear bunker-buster.
In addition, proponents highlight that the text does not require signatories to agree to end the nuclear arms race and disarm themselves of their nuclear arsenals, but rather requires them only to "pursue negotiations in good faith on effective measures relating to" achieving these goals, which are of a long-term nature. In their view, the lack of textual specificity in Article VI, coupled with the fact that the goal it enshrines is a long-term, even aspirational objective, suggest that compliance is most appropriately assessed by looking at the sum total of a state's actions relating to nuclear disarmament--its "disarmament balance sheet"--and not by looking at any single measure in isolation.[7] On this reading, ascertaining whether a state is in compliance with the text of Article VI requires a judgment as to whether the sum total of the state's behavior amounts to a good faith effort to negotiate on these matters. Thus, the relationship of nuclear bunker-buster research to U.S. obligations under Article VI should be assessed in the broader context of U.S. efforts to reduce its nuclear arsenal and to help Russia to reduce its own arsenal.
Defenders of the research also argue that there are currently no plans to deploy or even build a new nuclear bunker-buster.[8] A move in that direction would require Congressional authorization. Moreover, they contend, the $8.5 million proposed for FY 2006 is for nothing more than a feasibility study, and the amount of money being spent is miniscule in comparison to the $6.6 billion requested by the Bush administration for FY 2006 for nuclear weapons activities. In other words, concern about the nuclear bunker-buster research is overblown.
From the foregoing, defenders conclude that to the extent that nuclear bunker-buster research is viewed as a minor disarmament "debit" (but not necessarily illegal as such, in their view), on balance, other concrete steps the U.S. has taken towards nuclear disarmament[9]--disarmament "credits"--tip the disarmament balance sheet in favor of compliance with Article VI.
As noted above, the language of Article VI does not precisely identify what measures amount to a good faith effort, or what combinations of effort--some towards disarmament, perhaps others away from disarmament--satisfy its requirements. But critics of the legality of the research point out that the states parties to the NPT have agreed on a pair of ancillary documents that, in their view, provide additional guidance on what specific steps constitute evidence of compliance with Article VI: the 1995 Decision on Principles and Objectives for Nuclear Non-Proliferation and Disarmament, and more importantly and recently, the 2000 NPT Review Conference Final Document.[10]
The 1995 Decision on Principles and Objectives, produced as a consensus document at the 1995 NPT Review and Extension Conference, identifies three specific measures as "important" to the "full realization and effective implementation of article VI". These measures include: concluding the negotiation of a verifiable Comprehensive Test Ban Treaty (CTBT); negotiating a treaty that would end the production of fissile materials for weapons use; and "determined pursuit by the nuclear-weapon States of systematic and progressive efforts to reduce nuclear weapons globally." The 2000 Final Document, produced as a consensus document at the close of the 2000 NPT Review Conference, identified thirteen "practical steps for the systematic and progressive efforts to implement article VI" and the 1995 Decision.
Drawing on these documents, critics of the NPT legality of nuclear bunker-buster research argue that insofar as the United States has not fulfilled several of the thirteen steps,[11] it is on balance not living up to its Article VI commitments.[12]
With regard to nuclear bunker-buster research, the measure in Step Nine calling for nuclear-weapon states to achieve "a diminishing role for nuclear weapons in security policies" is especially relevant. Responding to the argument that concern about the nuclear bunker-buster research is overblown, critics typically cite the results of the last Nuclear Posture Review (NPR), the core strategic planning document for U.S. nuclear forces.
The January 2002 NPR recommended that nuclear weapons "could be employed against targets able to withstand non-nuclear attack (for example, deep underground bunkers or bio-weapon facilities)."[13] Critics argue that a pattern of nuclear weapons-related activities undertaken since then--including nuclear bunker-buster research, but also the Department of Energy's Advanced Concepts Initiative and Enhanced Test Readiness program[14]--supports an interpretation that these measures are early steps towards implementing new nuclear weapons capabilities, including a novel nuclear bunker-buster.
In their view, these activities imply an expanded role for nuclear weapons and the eventual resumption of nuclear explosion testing to verify that the weapon is capable of fulfilling the tasks envisioned for it. Insofar as these activities run afoul of the thirteen steps, critics argue that Article VI is violated. Critics add that such research also creates the conditions for a new nuclear arms race, which implicates Article VI's requirement to end "the nuclear arms race at an early date."
Defenders of the research might counter by pointing out that the Bush administration's FY 2006 budget proposal for work relating to the nuclear bunker-buster contemplates a total expenditure of $32 million through 2007, which they would argue is hardly enough to develop and deploy a new, technologically advanced nuclear weapon. In addition, the Department of Energy (DOE) proposed no funding for the Advanced Concepts Initiative for FY 2006, which defenders might argue further underscores that there are no immediate plans to produce a novel nuclear buster-bunker. Critics, in turn, might express skepticism over whether this forecast is reasonable, as the forecast made in DOE's FY 2005 budget proposal envisioned a total expenditure of nearly $500 million through FY 2009 and $82 million for the Advanced Concepts Initiative during the same period, yet there has been no apparent change in overall U.S. nuclear strategy to account for the large difference in the forecast.
Defenders of the NPT legality of nuclear bunker-buster research also point out that the 2000 Final Document was a statement of political consensus, and not a legally binding agreement.[15] Consequently, a failure to take any of the specific steps would not amount to a technical legal violation of Article VI, and should not weigh against a finding that the United States is in compliance with Article VI as a legal matter. Instead, they argue, the thirteen steps are political commitments, and are subject to revision on the basis of changed circumstances and new policies. Critics could counter that the thirteen steps codified a consensus interpretation of what Article VI requires today, and thus should be considered authoritative as a legal matter.
Ultimately, the legality of nuclear bunker-buster research appears to hinge on several difficult legal issues: whether compliance with Article VI is judged according to doing or failing to do certain things, or according to the sum total of a state's actions; whether and to what extent a particular policy or action by a state is a disarmament "credit" or a disarmament "debit;" whether the states party to the NPT are bound to fulfill some or all of the thirteen steps as a legal matter; and the legal import of a failure to fulfill one or more of these steps, to the extent they are legally binding.
About the author:
Andrew J. Grotto is Policy Analyst/Associate Scholar in National Security, Center for American Progress. Mr. Grotto is also an ASIL member. The views expressed herein are the author's alone.
[1] The dissuasion mission of the nuclear bunker-buster, however, is more of a strategic mission than a tactical one.
[2] In 1997, for example, the United States added the B-61 Mod 11 Nuclear Earth Penetrator--a tactical nuclear weapon--to the weapons stockpile.
[3] Memorandum by Linton F. Brooks, Administrator, National Nuclear Security Administration, FY 2004 National Defense Authorization Act, December 3, 2004, available at
[4] David L. Hobson, "Forward Thinking on Nuclear Policy," Washington Times, January 10, 2005. Available at:
[5] See, e.g., "Decision: Extension of the Treaty on Non-Proliferation of Nuclear Weapons," May 1, 1995, NPT/CONF.1995/32/DEC.3; "2000 Review Conference of the Parties to the Treaty on the Non-Proliferation of Nuclear Weapons, Final Document," 2000 NPT/CONF.2000/28 (May 22, 2000).
[6] See, e.g., Remarks of Steve Rademaker, Assistant United States Secretary of State for Arms Control (question and answer period), 2005 ACA Panel Discussion: "Fulfilling the NPT's Promise,", February 3, 2005. Transcript available at:
[7] See, e.g., Remarks of Steve Rademaker, Assistant United States Secretary of State for Arms Control, 2005 ACA Panel Discussion: "Fulfilling the NPT's Promise," February 3, 2005. Transcript available at:
[8] See, e.g., Remarks of Steve Rademaker, Assistant United States Secretary of State for Arms Control, 2005 ACA Panel Discussion: "Fulfilling the NPT's Promise," February 3, 2005. Transcript available at:
[9] United States Department of State, "Article VI of the Non-Proliferation Treaty." U.S. State Department Publication 11220, Bureau of Arms Control.
[10] See, e.g., Remarks of Roberto Abdenur, Ambassador of Brazil to the United States, 2005 ACA Panel Discussion: "Fulfilling the NPT's Promise,? February 3, 2005. Transcript available at:
[11] For instance, the United States has not ratified the Comprehensive Test Ban Treaty (Step 1); is not supporting a Fissile Materials Cut-Off Treaty that has verification provisions (Step 3); is not supporting the entry into force of the START II treaty, negotiation of a START III treaty, and withdrew from the Anti-Ballistic Missile (ABM) treaty (Step 7); identified new missions for nuclear weapons in its 2001 Nuclear Posture Review (Step 9); and opposed verification measures in the Strategic Offensive Reductions Treaty and the Fissile Materials Cut-Off Treaty (Step 13).
[12] See, e.g., Remarks of Roberto Abdenur, Ambassador of Brazil to the United States, 2005 ACA Panel Discussion: "Fulfilling the NPT's Promise," February 3, 2005. Transcript available at: The Arms Control Association is even more critical, raising doubts about U.S. compliance with most of the thirteen steps. See Arms Control Association, "Summary of U.S. Implementation of the '13 Practical Steps on Nonproliferation and Disarmament' Agreed to at the 2000 NPT Review Conference," April 4, 2002. Available at:
[13] Nuclear Posture Review, pp 12-13. Excerpts available at:
[14] The Advanced Concepts Initiative researched novel, low-yield nuclear weapons designs, and the Enhanced Test Readiness program aims to reduce the time needed to prepare nuclear testing facilities for possible future tests to 18 months from the current 24-36 months.
[15] See, e.g., Remarks of Steve Rademaker, Assistant United States Secretary of State for Arms Control, during Question and Answer period 2005 ACA Panel Discussion: "Fulfilling the NPT's Promise,", February 3, 2005. Transcript available at: