Michael KreponDiscriminate Deterrence

One paradox of nuclear deterrence has always been that whatever utility the Bomb provides is lost once the nuclear threshold is crossed, however large or small the boom. There is no bigger blunderbuss than a nuclear weapon atop a long-range missile. Smaller-yield message-senders have been created in the form of tactical nuclear weapons, but any advantageous battlefield use of nuclear weapons against a similarly armed foe requires heroic assumptions. Basic nuclear deterrence is measured by non-use. The derived benefits of “strengthening” deterrence by means of more discriminating or improved methods of delivery have been completely conjectural.

How much of a deterrent is a weapon that hasn’t been used on battlefields for almost 70 years? Deterrence strategists object to this formulation. They argue that, even without mushroom clouds, the Bomb has leveraged favorable outcomes in diplomacy, crises and wars.  These arguments do not withstand close scrutiny. The Bomb has indeed energized diplomacy to defuse crises – after exacerbating them. It has also reinforced the common sense of major powers not to fight full-blown conventional wars. Beyond reinforcing caution, the Bomb’s suasion is limited. It can’t override bad national decisions, local circumstances, and differentials in commitment to achieve preferred outcomes. The Bomb hasn’t proven its worth when nuclear-armed states square off against non-nuclear-weapon states, as is evident by a painfully long track record of conventional wars, limited wars, proxy wars and unconventional wars.

The quest to fine-tune deterrence to increase leverage above and below the nuclear threshold is nonetheless an endless project. As missile accuracies improved and warheads multiplied, thanks to MIRVs, targeting lists grew. Limited and not-so-limited options were added to massive targeting plans in the quest for leverage, advantage, or war-winning capabilities.

Deterrence benefits from limited nuclear options are based on two dubious presumptions — that escalation can be controlled and that an adversary will not skip rungs on the escalation ladder. Mental gymnastics have always been required to derive deterrence benefits out of plans for massive retaliation.

In the 1990s, the advent of precision-strike conventional capabilities promised greater diplomatic leverage and militarily effectiveness without crossing the nuclear threshold. But air power alone has always had limited effectiveness and suasion. “Prompt global strike” and hypersonic weapons are now advanced in the pursuit of more discriminate, effective deterrence. Their promise also rests on risky assumptions – that strikes will not mistakenly hit nuclear-armed or related targets, and that a foe will accept attrition without crossing the nuclear threshold.

Fred Iklé and Albert Wohlstetter led a study on ‘Discriminate Deterrence’ at the end of the Reagan administration. Their Commission on Integrated Long-Term Strategy report was released in January 1988. Contemporary readers will find no hints in this report that the Soviet Union, against which the Commission’s recommendations were primarily directed, was a house of cards. One example: “We will seek to contain Soviet expansionism in any region of the world.”

The Commission predicated its recommendations on this key finding:

To help defend our allies and to defend our interests abroad, we cannot rely on threats expected to provoke our own annihilation if carried out. In peacetime, a strategy based on such threats would undermine support for national defense. In a crisis, reliance on such threats could fail catastrophically for lack of public support. We must have militarily effective responses that can limit destruction if we are not to invite destruction of what we are defending.

How, then, to proceed? Here are some excerpts:

We must diversify and strengthen our ability to bring discriminating, non-nuclear force to bear where needed in time to defeat aggression. To this end, we and our allies need to exploit emerging technologies of precision, control, and intelligence that can provide our conventional forces with more selective and more effective capabilities for destroying nuclear targets…

We and our allies would rather deter than defeat an aggression, but a bluff is less effective and more dangerous in a crisis than the ability and will to use conventional and, if necessary, nuclear weapons with at least a rough discrimination that preserves the values we are defending…

The precision associated with the new technologies will enable us to use conventional weapons for many of the missions once assigned to nuclear weapons. The new technologies will work to strengthen the ability of our ground and air forces to defeat invasions. Particularly important in this connection is the prospective use of “low observable” (Stealth) technology in combination with extremely accurate weapons and improved means of locating targets. In the years beyond 2000, this combination will provide new ways to stop invading forces at great distances from the front lines.

Iklé and Wohlstetter were prescient in forecasting that the United States would pursue precision strike conventional capabilities, low observables, and replacing nuclear for conventional weapons against certain targets in strategic war plans. Even so, the U.S. track record of deterrence, dissuasion and compellence during the past quarter-century has not merited high marks. The awesome powers of nuclear weapons are greatly compromised in the real world. Diversified and more discriminating capabilities do not help when leaders and their followers are not amenable to deterrence. In these instances, what matters most is maintaining a firewall between nuclear and conventional capabilities.


  1. George William Herbert (History)

    As a theoretical and practical question, it’s been assumed either that things like Prompt Global Strike and low observable strike either do provide a stabilizing deterrence spectrum between low-nuclear and prior conventional actions, or enthusiastically don’t. I would like to see better summarization of the arguments either way and a more robust debate around it.

    My initial impression of PGS was positive (enough so that as an aerospace entrepreneur I bid on the DARPA Falcon launch vehicle), assuming you don’t strike across a nuclear armed state (i.e., if you attack Iran or North Korea over the south pole or some other trajectory not crossing Russia or China). Especially if you warn the nearby nuclear powers something’s in flight and not aimed at them.

    I am no longer sure that’s true, but the policy arguments seem driven by external viewpoints rather than deterrence issues intrinsic in the capabilities and doctrines.

    • Jonah Speaks (History)

      Specifically conventional PGS: Some PGS may have a spectacular ability to maneuver, e.g., traveling on a straight line toward Korea, then switching onto a new path toward China, Russia, or Japan. Assurances may not be enough to assuage fears: Perhaps clear limitations on numbers and inspections to ensure none are nuclear armed. Or perhaps non-development or non-deployment of the highly maneuverable versions.

    • George William Herbert (History)

      Regarding the maneuvering (particularly the hypersonic cruise / scramjet models), I believe that the *safest* models would be conventional ballistic reentry vehicles on long range ICBM / SLBM type launchers; SLBM is more likely to cause launch alarm, so ICBM “firing south” around the South Pole is the best of the best.

      You can add a little terminal maneuvering (a few km) for point strike precision maneuver without threatening neighboring countries.

      This has the advantage that it’s basically off the shelf tech. It’s less hypersonic-sexy, which is where the (currently R&D) money is coming from. Which is why it’s not the focal point of programs right now. But I think it’s best from a policy / stability and long term program cost point of view.

      Working up a robust position notification program / system to alert the other nuclear powers about CICBM / conventional PGS shoots would be even better, and is harmless even if the US and USS…Russia are about to Cold War again.

    • Jonah Speaks (History)

      Are current ICBMs capable of flying south and still reach plausible targets just south of Russia and China? Can they carry a conventional payload powerful enough to make the trip worthwhile? Or does this require additional research or acquisition?

      An alternative is to fly north, but only one at a time or in such small numbers that neither Russia nor China would feel it made any sense to “launch on warning” with a retaliatory attack before the conventional ICBMs have landed. Another alternative is a conventionally armed SLBM, with care to make sure the trajectory does not pass over Russia or China.

    • krepon (History)

      This from James Acton:

      Given the subject matter, I can’t not comment. 😉

      I agree with George on a lot of this. I’m not for or against CPGS, but I think the program has been driven by technology rather than strategy. I worry that Russian and Chinese will reflexively cause the US to accelerate development efforts without adequately thinking through their implications.

      In hindsight, the campaign to defund Conventional Trident Modification had the unfortunate effect of restricting debate almost exclusively to the problem of warhead ambiguity at the expense of other risks associated with gliders.

    • J_kies (History)

      All things PGS, conventional, are essentially non-rational at first principles. The issue ultimately is how you aim a weapon usefully that has a limited lethal footprint and is tied to ‘mobile’ soft targets by the ‘dinky’ warhead. If you have a good aiming system just give him/her a rifle and a posthumous ‘star on the wall’ for better / more assured effect.

      The working US systems in consideration began life as nuclear MARVs intended to penetrate Soviet ABM defenses. (SWERV) The Chinese system is attributed as a nuclear weapon system intended to defeat US BMD.

      Working CPGS is fundamentally dumb. The tyranny of physics dictate that long-way round shots aren’t ‘prompt’. The rocket equation dictates the resultant conventional payloads after reentry aren’t useful. People put nukes on ICBMs because no other payload was economically viable.

      To top the list; working on a weapon with no credible means to aim it is just wasted effort.

  2. Syed Muhammad Ali (History)

    Michael, I agree with you. History warns us that it is dangerous to assume that industrial interests or political ambitions will be subordinated to strategic wisdom. Contemporary technological trends in the US, Russia, China and India indicate that the political ambitions to dominate the world or their respective regions is leading the evolution and development of hypersonic cruise missiles, MIRV, MaRV, BMD and stealthy UCAVs. It is also unrealistic to assume that all future technological developments in the strategic realm will fit existing strategic concepts. Natural and Social Science needs to move on, in tandem. Best wishes, Syed Muhammad Ali.

  3. Jon Davis (History)

    I believe Prompt Global Strike will be most effective against non-nuclear states where we want to destroy a target currently assigned to a nuclear warhead. In the case with Russia and China, using PGS instead of nuclear warheads would reduce fallout and radioactivity of destroyed targets. I think it is important to move into this direction. It could one day make nuclear weapons more obsolete. However, I don’t see PGS as something that enhances deterrence. Deterrence is still reliant upon nuclear weapons.

  4. David R (History)

    Deterrence is the only function of nuclearweapon.. I hope. I can’t imagine even the most unstable person-leader of atomic empire to strike another and make Earth as we know vanish. Simple, I wanna live, so I can’t use it. But as deterrence it works well.