Michael KreponThe Highly Questionable Case for New Low-Yield Options

Quote of the week:

“We do not yet know surely in what proportion unreasonable fears and twisted hopes are at the root of the perverted policy now followed by the Kremlin. Assuming both to be involved, we must disarm the fears and disappoint the hopes.” — Henry L. Stimson, “The Challenge to Americans,” Foreign Affairs, October 1947

As we remember President George H.W. Bush’s deft diplomacy at the end of the Cold War, let us also take note of his actions lessening U.S. reliance on “tactical” nuclear weapons. Those who wish to pursue new low-yield nuclear options for sea-based delivery would reverse Bush 41’s wise decisions.

The stated reasons for doing so are to create more options to deter Russia from crossing the nuclear threshold and more ways to control escalation in the event this threshold is crossed. These initiatives, now focused on delivering low-yield warheads from Trident boats and attack submarines, have prompted sharp debate. While these arguments aren’t new, some of the camp dwellers are surprising.

A full, frontal debate on crossing the nuclear threshold is overdue because it’s been missing for quite a while. Instead, the debaters have focused on subsidiary matters, such as presumed Russian nuclear doctrine and what that might suggest for appropriate countermeasures. Another good reason to confront the issue of crossing the nuclear threshold head on is because conventional and nuclear counterforce capabilities are proceeding apace. They are now advancing in top-tier nuclear weapon possessing states and are coming within reach of second-tier states, as well, along with space-based sensors enabling such targeting.

So let’s return to basics. The debaters can agree that space and time for crossing the nuclear threshold are unalloyed positives — unless one wishes to carry out “splendid” pre-emptive strikes with nuclear weapons. Since this goal is beyond discussion in polite company — and in my view, both utterly reckless and unachievable against a well-prepared foe — let’s leave this aside.

Do new or more varied means of delivering “tactical” nuclear weapons provide for more time and space against crossing the nuclear threshold and, once crossed, enhance escalation control? The argument on the “pro” side is rooted in the presumed psychology of deterring a nuclear-armed foe: If the bad guy knows that the good guy has more options at the lowest rungs of the escalation ladder, then the bad guy will be more deterred from crossing the nuclear threshold. This would not only provide more time and space for crossing the nuclear threshold, but also enhance prospects for escalation control.

This argument is wobbly for multiple reasons. To begin with, most of those who seek more lower yield options to deter also seek war-winning nuclear capabilities, or at least advantageous outcomes in the event of a nuclear war. Here’s Bridge Colby, for example, in the November/December 2018 issue of Foreign Affairs:

“Washington’s task is clear. It must demonstrate to Moscow and Beijing that any attempt to use force against U.S. friends and allies would likely fail and would certainly result in costs and risks well out of proportion to whatever they might gain. This requires conventional military power, but it also means having the right strategy and weapons to fight a limited nuclear war and come out on top.” (Emphasis added.)

What does it take to fight and win a limited nuclear war against a well-armed and well prepared foe? Bridge has joined a distinguished line of strategists that have weighed in on the subject of fighting a limited nuclear war. None of his predecessors — Kissinger, Nitze, Brodie, Kahn, Wohlstetter, et. al. — have offered a sensible explanation for success. Some recanted their views. While escalation control in a limited nuclear war is to be fervently desired, the likelihood of its occurrence depends on whether both nuclear-armed adversaries are so chastened and shocked by witnessing mushroom clouds that they elect to seek a draw. If one or both seek advantage or victory, many more mushroom clouds would be required, and the greater the number of mushroom clouds, the less likely “victory” can be claimed.

Bridge has clarified to me that, in his view, “coming out on top” would mean fighting to a draw because mutual acceptance of the status quo ante would equate to a U.S. victory in peripheral regions around Russia and China. This is an important qualifier, but it still presumes that escalation can be controlled in a limited nuclear war. Escalation control presumes that well-armed nuclear adversaries can maintain an intact chain of command for forces fighting on a radioactive battlefield. Another critical assumption behind escalation control is that the level of trust and lines of communication between still-functional national command authorities in nuclear-warring states are sufficient to enable leaders to call off additional mushroom clouds.

These assumptions are not impossible to envision but may well be heroic. If the stakes at hand are so great and if trust or control have broken down to the extent that mushroom clouds have appeared on battlefields, then preventing more mushroom clouds would be extremely difficult — even assuming that both adversaries would accept a draw. These heroic assumptions become even more far fetched if one or both major powers seek advantage or victory rather than a draw.

Senator Jon Kyl and Michael Morell offer another argument for new low-yield options and new means of delivery. In their view, “The Russians believe we are not likely to risk a global thermonuclear war in response to a “tactical” nuclear attack by them. We must change that calculation; we must close the credibility gap.”  They presume to know what Russian nuclear war fighting plans are and how much Vladimir Putin is willing to risk by crossing the nuclear threshold at low yields. Even assuming they have extraordinary insight on these matters — and their reading of Russian nuclear war fighting doctrine is a matter of serious contention — they don’t explain why adding to the number and means of delivery for low-yield options would change Russia’s doctrinal and Putin’s war fighting calculations. To do this would presumably require more than tit for tat exchanges.

There have been fictional missile gaps and bomber gaps in the past. There was also a presumed nuclear war fighting gap during much of the Cold War because Moscow relied more on land-based missiles than Washington. Now we are being told there is a “credibility gap” relating to tactical nuclear weapons. The United States spends roughly $700 billion on defense. Russia spends approximately $70 billion on defense. If there is a credibility gap here, it’s not to the detriment of the United States.

Kyl and Morell propose to close the “credibility gap” by going back to sea with low yield options. Is their proposed means of response strategically sound? Would these responses add to or detract from deterrence? Are loading Trident tubes with low-yield weapons and torpedo tubes with SLCMs wise moves?

The locational secrecy of missile-carrying submarines could be compromised after firing one or more tactical nuclear weapons. Even if this were not the case, it is crucial in this scenario that Russia and China be able to figure out quickly either that they are not the intended target of attack or, if they are subject to attack from the sea, that they could discern that attacks are limited, thereby responding in ways the United States would prefer.

This doesn’t seem to be a sensible recipe for expanding time and space against uncontrolled escalation. Nor does it seem to be a sensible way to use launch tubes in missile carrying submarines. The number of ballistic missile-carrying submarines at sea is limited. To address a presumed “credibility gap” in tactical nuclear weapons by subtracting from strategic deterrence seems unlikely to provide a net gain in U.S. security. Likewise, the addition of nuclear-armed cruise missiles on board attack submarines would likely detract from their extraordinary conventional war-fighting versatility. If there is a need to shore up deterrence and war-fighting capabilities, the best way to do so would be to enhance conventional war fighting capabilities at sea while making it hard to find Trident boats.

There is another reason to endorse low yield nuclear options, as laid out by Scott Sagan’s essay in the November/December issue of Foreign Affairs. Scott, like Bridge, believes that, “by enabling a limited and smaller-scale U.S. nuclear response, lower-yield weapons would enhance the credibility of a U.S. threat to retaliate and this make aggression by Russia less likely.”

Scott extends his argument in two important ways by applying it to nuclear-armed states with small arsenals, against whom victory in a limited nuclear war is possible, and by introducing a crucial ethical dimension to this debate:

“Such weapons would make U.S. deterrence both more ethical and more effective — more ethical because they could be used to kill only leaders and military personnel responsible for acts of aggression, and more effective because they would make the possibility of U.S. retaliation inherently more credible.”

Let’s unpack this argument. If the use of nuclear weapons is unavoidable, then Scott is right in arguing that collateral damage should be as limited as possible, and that any use — initial or retaliatory — ought to conform to the laws of armed conflict. He is absolutely right that innocent people should not have to pay the consequences for the horrific acts of bad leaders.

Now let’s dig deeper: A war between a major power against a state with a very small nuclear arsenal can be won, but at what cost? And is the major power obliged to cross the nuclear threshold first, or even second in order to win?

First use against a much weaker nuclear-armed state poses a host of negative consequences. A preventive war employing preemptive nuclear strikes would end the seven decade-old norm of non-battlefield use — the linchpin of reducing nuclear dangers on a global scale. The negative ramifications of preemptive nuclear strikes by the United States against a weak, nuclear-armed foe would dwarf those of carrying out a preventive war with conventional weapons in Iraq. America’s global standing would plummet further, and the nuclear safety net — or what’s left of it — would be shredded. Carrying out preemptive strikes with low-yield weapons as opposed to strikes with hundred-kiloton-or-more yields would matter, of course, but the politico-military effects of a major power crossing the nuclear threshold first to defeat a weak state would be chart-topping, regardless of the yields employed.

Scott isn’t advocating preemptive U.S. strikes with nuclear weapons at any yields. What, then, about retaliatory U.S. strikes at low yields? He’s right up to a point: retaliatory strikes at low yields would be better than at higher yields. These options already exist. More could be added and steps could be taken to shorten their time of arrival by means of sea-based platforms, over the opposition of the U.S. Navy. The question in this dreadful event is whether precise and lethal strikes by conventional capabilities are available and sufficient for retaliatory purposes. If so, they would be preferable to the use of nuclear weapons at low yields.

Wise leaders in the executive branch and funders in Congress would focus on ways and means to deliver conventional capabilities to respond effectively to nuclear first use by a weak foe. A successful U.S. conventional response to nuclear first use by a weak foe could help repair the norm against battlefield use that we have come to rely upon. Nuclear retaliation by the strong against the weak would likely compound the damage if and when an outlier first crosses the nuclear threshold.

Granted, clarifying additive U.S. conventional power projection capabilities won’t be very assuring to a weak nuclear-armed state. But the message conveyed to a potential adversary as well as friends and allies would still be better than increasing the ways and means to use low-yield nuclear weapons beyond those already in hand. Bolstering accurate conventional capabilities would also address concerns about the ethics of battlefield use.

President Bush and his close advisors Brent Scowcroft, James Baker and Colin Powell got it right at the end of the Cold War: A United States whose power dwarfed that of the Kremlin was wise to encourage the removal from the field of tactical nuclear weapons that posed the hardest challenges of safety and security. It would be unwise to reverse Bush’s decisions. The smartest and most ethical approach to retaliation against a weaker foe is by conventional arms. We don’t need — and need to broadcast — new ways to deliver mushroom clouds with Hiroshima-type or lower yields.



  1. Mark Gubrud (History)

    In spite of so many arguing that the way for the United States to avoid nuclear war or escalation of the nuclear arms race is to develop more powerful non-nuclear (yet often novel) weapons, no one explains how it is that they expect deterrence to fail & nuclear-armed powers go to war, yet what is at stake to be of small enough importance to the enemy that they will capitulate on our terms despite still possessing, unused, nuclear weapons, which they could use whether to strike a major military blow, to enforce a stalemate or “escalate to deescalate.”

    I’m not claiming there is a strategy that the non-nuclear loser can use to achieve a victory through nuclear use, but I think it is at best a coin toss whether the non-nuclear loser accepts defeat or resorts to nuclear use under whatever theory, particularly in a strategic-level war which already includes intended or inadvertent attacks on nuclear weapons, infrastructure and C2.

    It is too convenient for nuclear arms controllers to say we should rely on “conventional” deterrence. When “deterrence” becomes the pursuit of military supremacy the result is an arms race which is just as destabilizing for its non-nuclear as for its nuclear components.

  2. oliver (History)

    Mr. Krepon,
    any use on the battle field, regardless of yield, of nuclear weapons will only lead to one result: MAD!!!!

    Cheers, Oliver

  3. John Chick (History)

    Good piece, as always. As a novice (current student in Nuclear Deterrence-Harvard Extension School), I ask your patience if I say anything too stupid . Regarding your assertion that a preventive war employing nukes against a weaker nuclear armed state would be politically disastrous for the U.S., I’m not so sure, depending on the circumstances. First, is any state with nuclear weapons and the means for delivery “much weaker”? Second, it should be safe to assume that we would strike first only if it felt a nuclear strike against us was imminent Therefore, the U.S. could take the risk of conventional strikes, hoping they destroy all of the weapons before even one gets away and flies toward the U.S. – or it could employ low yield nukes to better ensure all are destroyed. Perhaps there’s no assurance using either conventional or nukes, but it would seem to me that using nukes would make it more likely. As you say, “The question in this dreadful event is whether precise and lethal strikes by conventional capabilities are available and sufficient for retaliatory purposes. If so, they would be preferable to the use of nuclear weapons at low yields”. That would be the U.S.’s assertion to the world community after the fact. If the U.S. could clearly demonstrate, that the choice was between possible overkill and losing Los Angeles, then I think the world at large would understand the logic of self-defense. Our enemies wouldn’t, regardless.

    • Jonah Speaks (History)

      In this context, a “weaker” nuclear state is presumably one with significantly fewer nuclear weapons and significantly weaker conventional forces. There is a subtle distinction here between a stronger state that is pre-committed to no nuclear first use, and one (such as the U.S. currently) which is ambiguous on this point.

      If the U.S. pre-committed to no first use of nuclear weapons (e.g., through Congressional legislation), an opposing nuclear state would have maximum incentive to refrain from nuclear first use. This is partly because it would have “no moral excuse” for starting a nuclear war, and partly because of deterrence: The weaker state would fear nuclear retaliation for starting a nuclear war, even while knowing that nuclear retaliation could have been avoided simply by not using nuclear weapons.

      While it may “be safe to assume that we would strike first only if [we] felt a nuclear strike against us was imminent,” it is not safe to assume that we would have this much fore-knowledge about what an adversary will do. Any such decision would be based on fear. We can reduce this fear (both ours and theirs) by pre-committing to no nuclear first use.

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