49. Memorandum From Jan Lodal of the National Security Council Staff and the Counselor of the Department of State (Sonnenfeldt) to Secretary of State Kissinger1


  • Including SLBMs in an Equal MIRV Throw Weight Proposal

You have indicated on several occasions that you believe inclusion of SLBMs in a MIRV throw weight limit proposal is basically a “tactical” issue; the Soviets will certainly insist that we do so, and, intellectually, we have no good arguments for not including them. Thus, you have indicated that we should leave it up to Ambassador Johnson as to when and how he includes SLBMs.

We disagree strongly with this approach. Although we have outlined our reasoning in several other memos and in past meetings, this memo attempts to put all our arguments in one place.

The main argument against including SLBMs is that they represent our major bargaining chip and leverage in SALT II. Much as we traded our ABM capabilities to get Soviet limits on ICBMs in SALT I, success in SALT II is likely to require trading some of our momentum in SLBMs for Soviet limitations on their ICBM programs, and SLBM MIRV throw weight limits at reasonable levels represent de facto limits on Trident.

Our major MIRV throw weight is planned for SLBMs. Minuteman III will have 1.3 million pounds of MIRV throw weight, but Poseidon alone will have 2.1 million pounds. A full Trident program would add an additional 1.3 million pounds—an amount equivalent to our entire [Page 173] land based ICBM MIRV throw weight—to the Poseidon base, for a total of 3.4 million pounds of sea-based MIRV missile throw weight. If we tabled a proposal initially with a throw weight level high enough to permit our full SLBM program plus Minuteman III (4.7 million pounds), it would be almost impossible to argue for a low ICBM sublimit. The Soviets would probably agree to the 4.7 million pound level, but would insist on taking the bulk of their throw weight in ICBMs to offset our SLBM advantage. This would lead to a strategically meaningless agreement. Perhaps we will eventually have to fall back to something like this; nevertheless, we should first attempt to get a strategically meaningful limit on ICBMs, something we do not believe we could negotiate if we started with the high level required to give us our full SLBM program.

Of course, we could start with a lower total throw weight. However, a lower level would constrain us to deploy Trident only as a replacement for Poseidon. Since we could never convince Congress to replace perfectly good Poseidon boats with Trident, this would obviously kill the Trident program. Thus, a lower total level, while perhaps permitting us to negotiate a more meaningful ICBM limit, would do so at the cost of our Trident program. We might very well want to do this at some point, but we should not do it in our initial proposal.

There are three other reasons why we believe we should hold up introducing SLBMs into the MIRV throw weight deal:

(1) Verification of SLBMs is more complex. We will almost certainly have to go to a categories or “block” approach for SLBM verification. There seems to be no way to verify deployment of SLBMs within a single category. However, including SLBMs initially, with their associated categories approach, would make it much harder to avoid a categories approach to ICBMs.

(2) Throw weight is harder to measure for SLBMs. It’s much easier to trade off range for payload on SLBMs. For example, our Trident I missile could have almost 50% more throw weight than Poseidon. It will not have more throw weight only because we are using all of the additional thrust capability of the missile to increase its range, not its throw weight. We could end up in endless arguments with the Soviets about how to measure SLBM throw weight. Such arguments could prejudice our entire throw weight concept for dealing with MIRV. We would be much better off if we could get agreement in principle on ICBMs first.

(3) MIRVs on SLBMs are simply not the threat they are on ICBMs. You are familiar with most of the reasons why this is the case. SLBMs are much more difficult to control, their accuracy is not as good as ICBMs, and they carry smaller warheads than Soviet ICBMs. Thus, SLBM MIRV throw weight limitations are considerably more cosmetic and less strategic than are ICBM limits.

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In conclusion, we agree that SLBMs will eventually have to be thrown in. We might very well have to allow the Soviets an edge in ICBM throw weight to offset our edge in SLBM throw weight. Likewise, we might have to limit Trident in return for restraints on Soviet ICBM programs. However, we believe the best way to get to this point is to start by pressing hard for limits on ICBM MIRV throw weight. We can certainly make it clear to the Soviets that we are willing to consider SLBMs if we can get agreement in principle on the agreed MIRV throw weight concept. But we should not start with a specific SLBM program. It leads us down many slippery slopes which can be much better dealt with if we first have agreement in principle on equal MIRV throw weight.

We believe these considerations are particularly important with respect to what is put on the table in Geneva. Even if you wish to open the issue of SLBMs relatively early in your channel, it could be quite dangerous to let the delegation get out in front of you in Geneva.

  1. Source: National Archives, Nixon Presidential Materials, NSC Files, Box 891, SALT, SALT TWO–Geneva–January, 1974. Secret; Sensitive; Completely Outside the System. Sent for urgent information.