Jeffrey LewisResuming SLCM Data Exchanges

I was in DC briefly this week to participate in a workshop hosted by the Carnegie Endowment.  James Acton asked me to propose a US-Russia confidence-building measure, which offered the welcome opportunity to make a suggestion I’ve been kicking around for awhile: The United States and Russia should resume the data exchanges on deployed nuclear-armed sea-launched cruise missiles that ended with the expiration of START.


A confidence-building measure is, in my view, a bit more than the name implies. I will gleefully ignore the very large literature on confidence-building measures.  Instead, I propose a narrow definition: a confidence-building measure is one that helps the parties resolve a difficult issue in the context of bilateral arms control negotiations. The measure need not resolve that issue by itself, but may create confidence that further negotiations will result in a mutually beneficial resolution.

In the current context, we certainly need confidence building measures.  Tom Donilon, the national security adviser, announced that the Obama Administration intends to seek, in the next round of negotiations with Russia, a agreement that would “include both non-deployed and nonstrategic nuclear weapons.” Administration officials have taken to calling this approach “The Whole Enchilada.”

The Russian palate is of course, famously bland.  One does not need to be a hardened skeptic of arms control to ask whether our Russian interlocutors might find an enchilada too spicy for their taste.  The Administration is, in essence, committing to resolve every difficult issue that could not be agreed during the nine-year negotiation of the original START agreement, less than two years after it was unable to preserve some of START’s more intrusive verification elements.  In response to my skepticism, some of my colleagues in the arms-control community have suggested that there is something to be said for pursuing the right idea, even if it takes rather longer than one might hope.  Try being constructive instead of a jerk, they argue, and propose confidence-building measures that might solve some of the objections you’ve raised.

Fair enough.


One of the more difficult problems in the negotiations over the original START treaty — and one will need to be resolved in a “Whole Enchilada”-style New START follow-on — relates to long-range sea-launched cruise missiles (SLCMs) such as the Tomahawk and the SS-N-21.  The late Office of Technology Assessment prepared a nice summary of the challenges in limiting SLCMs with arms control, Monitoring Limits on Sea-Launched Cruise Missiles.  (Our own Michael Krepon was on the advisory panel.)

The Soviet sought limits on sea-launched cruise missiles in the START treaty, largely for the same reason that they found the deployment of Pershing II missiles alarming. Modern LACMs have long ranges  — 2500 km for the SS-N-21 — high accuracy and stealth capabilities that give nuclear-armed cruise missiles deployed at sea a distinctly strategic quality. For those of you who remember Mathias Rust, the Soviet leadership must have worried that the first notification they would receive of a decapitating SLCM attack on Moscow would be a very bright flash. (George Lewis and Ted Postol wrote a nice summary of the stability problems induced by SLCMs for the Bulletin of the Atomic Scientists called “SLCMS — Ignored, then Stored.”)

The United States opposed including SLCMs in the START treaty because it intended to deploy large numbers of conventionally armed SLCMs. The same ships could carry SLCMs with either conventional or nuclear warheads, raising all the classic challenges associated with verifying limits on nonstrategic nuclear forces available for use by general-purpose forces.  To a first approximation, a verifiable limit on SLCMs would require a constraints on all SLCMS, including conventional ones, something the United States was understandably reluctant to do. (It is, of course, possible to imagine very intrusive measures that would allow each party to determine whether a particular cruise missile was armed with a nuclear weapon or not.  This debate produced one of the all-time great NGO efforts – NRDC actually secured access to a Russian warship in the Black Sea to demonstrate that gamma-ray measurements might provide a feasible means of verifying that nuclear weapons were not aboard naval vessels.)

In the end, the United States and Soviet Union agreed to exclude SLCMs from the START treaty, instead issuing “politically binding” declarations under which the parties would deploy no more than 880 nuclear-armed sea-launched cruise missiles aboard naval vessels and declare, on an annual basis, deployments for each of the next five years. The important concepts were “deployed” and “nuclear-armed.”  Conventional SLCMs or nuclear-armed systems in storage were not covered.

Between signature and entry into force, the Soviet Union collapsed.  That process generated the so-called Presidential Nuclear Initiatives regarding “nonstrategic” nuclear weapons.  The PNIs had some impact on nuclear-armed SLCMs, though perhaps not unambiguously so.  The United States withdrew all of its nuclear-armed SLCMs as part of the President Bush’s September 1991 unilateral pledge that started the “Presidential Nuclear Initiatives.”  Soviet and Russian statements were ambiguous, but the United States expected Russia to declare “zero” deployed nuclear-armed SLCMs under the START data exchanges.  I suspect the Soviets (and Russians) did, in fact, declare zero, if only because I would expect any other number to leak.  But I don’t know that.  I have copies of the Russian declarations for START, but not the SLCM declarations.  (In principle, this ought to be knowable.)

In any event, the US and Russian declarations ended ended with the expiration of the START treaty.  The Bush and Obama Administrations appear to have made little or no effort to preserve them. Indeed, as the START treaty neared expiration, the United States submitted 4, 3, 2 and then 1 year declarations.  The last US declaration, in case you want to know what one looks like, is available in the Wikileaks cable dump.


It will not be possible to ignore nuclear-armed SLCMs in a START follow-on agreement.  The elegant solution under START — simply deferring the issue with politically binding declarations — is not possible if the United States seeks a comprehensive agreement.  SLCMs, or at least nuclear-armed SLCMs, will have to count for something.

Although the United States has no nuclear-armed SLCMs, the situation with Russia is more complicated.  In 2006, then-Defense Minister Sergei Ivanov claimed that three “multipurpose” (i.e., attack) submarines were on combat patrol with nuclear weapons.  Russia is building a new nuclear-powered attack submarine and appears to be developing a new family of cruise missiles, which could presumably arm this new system. Nuclear-armed cruise missiles are an excellent candidate for the unspecified “proper response” that Putin indicated would be coming in reply to US missile defense deployments in Europe.

Even if Russia does not deploy nuclear-armed sea-launched cruise missiles, a New START follow-on will need to verify “zero” in a way that provides confidence for our allies in NATO.  I happen to believe that SLCM verification is not hopeless, given an INF-like verification regime. On the other hand, the INF treaty is hardly in great shape largely because of the sort of asymmetries that might drive Russia to consider resuming deployments of nuclear-armed SLCMs.

And then, there are the geniuses in Russia marketing a containerized cruise missile system.  Recent Russian advertisements showing cruise missiles hidden in shipping containers are unlikely to help win Senate ratification of any future agreement. Although the cruise missiles for sale are are much shorter-range (300 km rather than 3,000 km), the producer of the Club-K missile system also makes the SS-N-21.

When this or some future Administration goes to negotiate “The Whole Enchilada,” the issue of nuclear-armed long-range Sea Launched Cruise Missiles is going to be a royal pain in the ass.


The simplest step is to resume the data exchanges under a politically binding agreement identical to the one that lapsed with the START treaty.  My proposal would be to use the identical text from the START process, even though the limit of 880 deployed nuclear-armed SLCMs is way too high.  (When I pointed out that 880 was too high, one former START negotiator laughed and told me “It was way too high then!”)

Now, Russia may come back and want to count all long-range SLCMs (since we’re locked into zero nuclear-armed ones and they are equally worried about the conventional ones.)  Counting all SLCMs would probably require some number other than 880.  I don’t have a problem with declaring deployed SLCMs as long as the limit is high enough that it doesn’t interfere with conventional operations.  The real value is not the numerical limit, but the annual five-year declarations.

This ought to be politically feasible.  The United States and Russia exchanged these data every year for the life of the START treaty and the world did not end.  Moreover, Senator Jon Kyl (R-AZ) introduced an amendment during the New START ratification process (Kyl Amdt. No. 4860) that would have required the President to resume SLCM data exchanges with Russia.  Kyl’s amendment was defeated as a delaying tactic and some Senators expressed legitimate concerns that the amendment was drafted in haste.  (The amendment required a legally binding agreement, in contrast to the politically binding exchange under START.  When asked about the difference, and reminded that the United States had sought to avoid legal limits on SLCMs, Kyl was nonchalant: “Whether you call it binding legally or binding politically, in any event, I wish to see it done…”)

Whatever one thinks of the wording of the amendment, or the motives for offering it, the resumption of SLCM data exchanges is a good idea in principle. If the retiring Senator from Arizona wishes to lend his support to an effort to resume those exchanges, the Administration should welcome it as a step that would strengthen the existing New START treaty and help build confidence that the Russians might someday swallow the Whole Enchilada.

Declarations alone, of course, don’t solve the problem of controlling nuclear-armed SLCMs.  But resuming the SLCM declarations from START makes sense as the first of what might be several confidence-building steps on a path to resolution.  One of the “intrusive” ideas for monitoring SLCM limits in the late 1980s was to tag each cruise missile with a unique identifier (see: George N. Lewis, Sally K. Ride, and John S. Townsend, “Dispelling Myths About Verification of Sea-Launched Cruise Missiles,” Science, November 10, 1989).  Tagging actual missiles was considered an unacceptable intrusion during the late stages of the Cold War, but the New START agreement provides for SLBMs and ICBMs with unique identifiers.  This was a major achievement for the New START team.  Tagging SLCMs is now, at least in principle, a conceivable step based on the experiences from tagging SLBMs and ICBMs. Tagging SLCMs a bit too far for a first step, but New START is an encouraging sign that, if declarations could resume, the conversation about controlling SLCMs might continue in interesting and productive ways.

For now, I would be happy if we could simply get back to square one andP resume the SLCM data exchanges that ended with the expiration of the START treaty.


  1. Captain Ned (History)

    Pershing II cruise missiles??

    • Jeffrey (History)

      No, I didn’t write that did I?

    • Jeffrey (History)

      Yep, I wrote that. God damn it. I fixed it. Can’t wait to see what other stupid things I wrote in a rush.

  2. Jon (History)

    I think we should take it one step further. Just like we did with retiring the Tomahawk TLAM-As, we should remove the W80-1 warheads from the AGM-86Bs and put them in central storage as part of the reserve stockpile, and convert the alcms to conventional only. Perhaps if we then take the stance that we won’t field any nuclear cruise missiles whether by sea or by air, Russia may become more flexible in any future negotiations. And removing the B-52H from the nuclear mission is not going to diminish our deterrent. It will only provide for a stronger conventional Global Strike mission. Maybe just without the “Prompt.”

    • anon (History)

      I think that any proposal based on “if we do this, then the Russians will be more accomodating with that” is somewhat naive. Russia will do what is best for Russian national security. Its current interest in SLCMs, both conventional and nuclear, has nothing to do with the presence or absence of U.S. nuclear-armed cruise missiles, either air- or sea-based. For Russia, SLCMs are a relatively low-cost way of extending the reach of the Russian Navy, which helps overcome both the myriad of other conventional weaknesses in the Russian military and the sense of national military decline. If one wants to take a darker look at it, one could also claim that it is a part of Russia’s interest in challenging NATO on the high seas (I don’t necessarily take a dark look, but I know many who do…)

      I’ll have to spend some time chewing on the idea of SLCM data exchanges. I haven’t thought about that much in the last 20 years….

    • Jeffrey (History)

      I think my view is closer to Anon’s than Jon’s, though paradoxically that is why I support a data exchange as a first step toward eventually attempting to control nuclear-armed SLCM deployments.

      Russia may (or may not) deploy some number of nuclear-armed SLCMs. We are not likely to replace TLAM/N. We will want, as part of any future agreement, to limit Russia’s nuclear-armed SLCMs and to monitor that limit. (I think this is desirable even if we don’t go for the Whole Enchilada. If we do, by definition we need to control nuclear-armed SLCMs.) The only path I can see toward that outcome starts with a data exchange, before moving to more intrusive confidence-building measures. I am not, actually, optimistic.

      No doubt, Russia will want us to declare the total number of deployed SLCMs, not just nuclear-armed ones. That might be enough to tempt the Russians. Or it might not. I don’t have an immediate objection to agreeing to declare the number of deployed SLCMs provided that the declaration was not a legally-binding limit. (I suspect the total stockpile number is more sensitive since one ought not advertise depletion, but oddly I seem to recall seeing that number in a budget document recently.)

    • Jon (History)

      I am not opposed to data exchange of our conventional slcms with Russian nuclear slcms. I think we must stear clear of putting more conventional arms limitations in any future agreement. I am not opposed to the conventional warhead limit on icbms or slbms because I think it is a really bad idea to put conventional weapons on these delivery vehicles, there is no good way to differentiate between a conventional or nuclear attack. But this goes along with my belief on cruise missiles. I think they lend themselves as perfect conventional weapons and any future agreement maybe should limit them as such.

  3. Jon (History)

    Perhaps it is naive to assume the Russians would be more flexible with data exchanges with slcms if we went totally conventional with all of our cruise missiles. But in support of my belief, the Russians will field weapons based on perceived threat. And if we continue to reduce our weapon systems, they may find it is also strategically and financially smart to field less as well. What we want to prevent is a Russian build-up after they retire their legacy systems. And we have to make it appealing to bring in more issues on future negotiations, such as slcm data exchange, tactical warheads, total warheads, delivery vehicles, etc.

  4. JohnLopresti (History)

    The NRDC ‘experiment’ observed one flaw in the detection process: namely, the “high resolution” gamma ray detector works only if the inspected missle was unshielded. Without shielding the distance of detection was stated as ~20′ for ‘energetic’ gamma radiation from U235 and or Pu239. [OTA report page, 1992, p.16 in the document, p.21 in the PDF; see also footnote 49 on that same page).

    Suppose the containerized system shown in the blogpost image included internal shielding within each container…

    I liked the name of the NRDC selected cruiser, Слава “Praise”.

    • John Schilling (History)

      Shielding a 40-foot shipping container sufficiently to reduce the gamma ray detection distance by a factor of two, would require just about thirty metric tons of lead.
      Coincidentally, this is the rated net capacity of a 40-foot shipping container; possibly detection of containers with shielding+missiles would be practical by way of noting that e.g. the truck’s suspension has bottomed out…

      One could of course just shield the individual warheads; for that a mere half a ton of lead would do the job. Also coincidentally, the total payload capacity of a Klub-M is about half a ton.

      Probably one could do somewhat better with an intermediate scheme, with a blanket around the launch tubes at about the position of the warheads plus shadow shields elsewhere in the container to catch the leakage
      and scattered radiation, but this would not be a trivial scheme – particularly since you’d want to do better than just reduce the detection range by half.

      And, as the NRDC noted, all bets are off if you use active detection, hitting the container (or whatever) with a brief neutron pulse and looking for the temporally coincident gamma spike. This also is not a trivial undertaking, intrusive and prone to counterclaims that we are irradiating the Russian’s precious bodily fluids or whatever.

      But, generally speaking, clever people with a bit of access can make it much harder for even clever people on the other side to hide illicit nuclear missiles.

  5. JohnLopresti (History)

    re John Schilling’s helpful observations. I agree with all of that. After having examined the OTA report, the NRDC documentation was an interesting, first-person account. Interestingly, the US showed up with a Ge-based passive detector that was more successful than the comparable Russian instruments, according to my reading of the account; however, the Russians also demonstrated a passive neutron detector fitted in a helicopter which achieved better range of detection, albeit with less resolution for storage areas below the ship’s deck.

    Still, all of these events evidently were 22 years ago, and I would anticipate advances since, in both shielding and detection apparatus.

    For now, apparently we remain faced with the optimal physics of the Pb nucleus for shielding. However, I am reminded that in a wholly different area of materials science, ‘transistors’, the form factor those 22 years ago was quite different from the sub-micron physics of chip fab today. This is a lot different from 10′ thick Pb walls for shielding.

    Perhaps Pb’s properties are intrinsically and incontrovertibly a factor in the shielding equation now, and ongoing. I would have to look farther into the literature for the answers to some of those questions.

    As the reports, and John Schilling, observed, active detector design is a different modality, with different logistical obstacles.

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