253. Memorandum From Philip Odeen and Helmut Sonnenfeldt of the National Security Council Staff to the President’s Assistant for National Security Affairs (Kissinger)1


  • SALT and New SLBM Intelligence

There have been some recent events which should affect any consideration of whether or not to give up trying to get SLBMs included in the interim freeze.

  • —Because of some mistaken estimates by the intelligence community, our present SLBM proposal is not as attractive as we imagined and may figure in Soviet resistance to SLBM inclusion.
  • —The Soviets have shown some flexibility at Helsinki on SLBMs. As Gerry Smith has pointed out, rather than flatly ruling out the inclusion of SLBMs, the Soviets now say it is “sufficient” to have an ICBM-only freeze. Whether this is just a milder form of rejecting [Page 759] SLBMs or whether it signals a Soviet change in position is still unclear.

Given the above, before we face the issue of dropping SLBMs, we should consider offering the Soviets freedom-to-mix from ICBMs to SLBMs.

The Mistaken Intelligence Estimates

Until the past few weeks, the intelligence community had unanimously informed us that the Soviets had accelerated Y-class submarine construction and that they had started construction of the 42nd Y-class submarine (which would have given them an advantage in modern subs and SLBMs).

These estimates were conveyed to the Soviets through press leaks and comments by Gerry Smith to Semenov.

The intelligence estimates were wrong—significantly inflated.

The intelligence analysis had correctly spotted some anomalies in the order of new Y-class launchings from the construction yards. They interpreted this to mean an acceleration in construction.

In fact, as the latest photography makes clear, the Soviets were in the midst of a production slowdown as they were making extensive modifications in the new Y-class submarine. These modifications included:

[1 paragraph (5½ lines) not declassified]
Lengthening of the submarine by 25 feet (to a total length of about 150 feet). The purposes for this lengthening are still unclear. It is in the propulsion area of the boat which suggests some measures are being taken to quiet the engine noises. Additionally, it might be to provide more ballast to offset the larger missiles being added.

There is still some uncertainty about the number of Y-class subs operational or under construction. CIA believes the number is at least 2 boats and probably 3 boats below what we were estimating last Fall.

Moreover, there is still considerable uncertainty about the number of SLBMs now under construction since the 12 boats now in the construction halls could have 12 launchers or 16 launchers. CIA has looked at the previous photography of components which have entered construction halls and believe at best 2 of the boats will have 16 small launchers and probably at least 6 will have 12 large launchers; the load on the remaining 4 boats is uncertain.

One result of all this is that we have confused the Soviets with our specific, but inflated figures.

Our SALT Position

Most important our proposals to include SLBMs in the interim freeze have not been as attractive to the Soviets as we believed.

[Page 760]

Our current SLBM proposal sets as a freeze date the date of signature of the interim agreement and allows replacement of old SLBMs and boats with new ones. While we had some inkling last month of over-inflation in our estimates, we still were not aware of the extent. Consequently, assuming signature would occur the end of May, we estimated that the proposal would allow the Soviets to complete 43–45 Y-class subs and 690–720 Y-class SLBMs operational or under construction. Additionally, the Soviets could replace their 100 launchers in G and H-class boats with an equal number of new launchers in Y-class subs.

In fact, excluding G and H-class replacement, the Soviets probably are now allowed to complete only 41 Y-class subs and about 604 Y-class SLBMs. This is parity in new subs, but slightly less than parity in SLBMs. By allowing replacement we give the Soviets a slight numerical edge in subs and SLBMs. However, this assumes that the Soviets would want to replace the 100 SLBMs on their recently modified G and H-class subs.

[1 paragraph (3½ lines) not declassified]

Consequently, there seems to be increased reason for suggesting some form of freedom-to-mix from ICBMs to SLBMs.

  • —We might limit it, at least initially, to replacing soft-pad ICBMs (the Soviets have 134) for SLBMs.
  • —Alternatively, we might limit it initially to replace silo-launched ICBMs. (The Soviets have 75 SS–7s and SS–8s in silos.) This makes freedom-to-mix less attractive to the Soviets since they get no credit for replacing soft pads.

Freedom-to-mix does have its problems. It essentially allows unequal aggregates for each side. The JCS oppose it on this basis.

However, as we have argued before, getting SLBMs included in the interim freeze is worth the cost of allowing freedom-to-mix.

Attached is a revised chart2 which gives the latest estimates of the number of Y-class subs and SLBMs allowed under our present proposal and by allowing freedom-to-mix.

  1. Source: National Archives, Nixon Presidential Materials, NSC Files, Box 882, SALT, SALT talks (Helenski) [sic], Vol. 17, January–April 1972. Top Secret. Sent for urgent information. Sonnenfeldt did not initial the memorandum.
  2. Attached but not printed.