228. Memorandum From Philip Odeen of the National Security Council Staff to the President’s Assistant for National Security Affairs (Kissinger)1
- Strategic Analysis of the OSD ABM Proposal
This memorandum analyzes the strategic issues underlying the OSD ABM proposal for SALT. (We have already written you extensively about the negotiating and political issues.)2 On a strategic level, the OSD proposed deployments of Hard-Site Defense would:
- —Assure the survivability of no more than an additional 100 Minuteman (and possibly less).
- —Provide some strategic benefits to the Soviet Union, though the extent of these is very sensitive to the number and location of the ICBM fields protected.
The First Stage
The initial ABM deployment allowed would be one Safeguard site for the U.S. at Grand Forks, and Moscow ABM for Soviets.
- —We would therefore have to stop the construction now underway at Malmstrom.
One Safeguard site for the U.S. provides no substantial protection of our retaliatory forces and very limited population defense.
Moscow ABM provides the Soviets with protection of the area (including about 25% of the Soviet population and 35% of the industry) against accidental or very limited attacks by missiles.
The Second Stage
The second stage of the OSD proposal would allow, after three years or upon mutual agreement:
- —The U.S. could deploy an ABM defense of Washington.
- —The U.S. could deploy Hard-Site Defense (HSD) at Grand Forks.
- —The Soviets would be allowed to deploy HSD at one ICBM field which meets agreed geographical limitations. (OSD had earlier proposed that the Soviets be allowed to protect equal numbers of silos as the U.S., e.g., 150. This would mean that the Soviets would be allowed to protect as many as 3–4 ICBM fields since the Soviets would have fewer ICBMs in each field.OSD now believes that the Soviets would accept defense of one ICBM field.)
- —For each side, Hard-Site Defense would include at least 1,000 short-range interceptors and many short-range ABM radars.
1. The U.S. Deployment
If the U.S. decided this year to plan on deployment of HSD and made prompt funding decisions, actual deployment would begin by late 1977 and could be completed by about 1979–80.
- —This assumes using the Army HSD system which involves modified Sprints and a new radar. Any major changes in the Army plans would further delay deployment.
- —This late deployment date means that the threats to Minuteman which should be considered in evaluating the efficacy of HSD are those which the Soviets could deploy by the 1980s.
There are essentially three scenarios the Soviets might follow with respect to their threat to Minuteman:
- Scenario 1: The Soviets may develop their counterforce capabilities slowly, so that at least 300 Minuteman could survive into the 1980s. In this case, we would not need to start deploying Hard-Site Defense for many years, if ever.
- Scenario 2: The Soviets might make considerable improvements in their offensive forces so that they could destroy 800–900 Minuteman [Page 679] by the late 1970s. (Such improvements would include better accuracy, MIRVing, and increased yield-to-weight ratios.) Note that there would still be about 100 or more survivors even without HSD.
If HSD were then deployed according to the OSD proposal, the system could assure up to 100 additional Minuteman survivors.
- —The number of additional survivors is 100 rather than the full 150 Minuteman at Grand Forks because, facing a HSD system with 1000 or so interceptors, the Soviets could overwhelm it by using enough RVs and still destroy most of the missiles at Grand Forks. However, by using up some of their RVs to exhaust our defenses the Soviets would have fewer RVs left to destroy silos at all the ICBM fields (including Grand Forks).
- —After deployment of 1000 interceptors at one site, additional ABM interceptors provide no substantial increase in the number of Minuteman survivors. An expansion of the HSD defense to two ICBM fields the number of surviving Minuteman missiles increases by at least 50%. (However, OSD does not recommend that we seek HSD protection of two fields. Presumably this is because the Soviets would argue for something like equivalent protection of 350 ICBM silos. This, given the size of their ICBM fields, would allow them protection of 5 or more ICBM fields, thereby greatly increasing the danger of the Soviets developing a territorial defense.)
- —The number of additional survivors would be smaller if the HSD system did not work as planned. (This problem is discussed later.)
3. Scenario 3: The Soviets could by the 1980s develop and deploy a counterforce threat which could reduce the number of Minuteman down to less than 50 even if we deployed OSD’s proposed HSD . Essentially, the Soviets would deploy enough warheads (through extensive MIRVing) to be able to overwhelm our defenses and still have sufficient warheads and accuracy to destroy the undefended Minuteman.
- —These threats do require the Soviets to expend considerable resources on their ICBM force. They are generally beyond what the NIE projects as the more likely trend of Soviet threat development.3
- —OSD recognizes that their HSD can be overwhelmed and most Minuteman destroyed. In reply, OSD argues that the U.S. would invoke the supreme national interests clause to withdraw from the SALT agreements and thereupon take more decisive actions, such as more extensive deployment of HSD.
Hence, only in a broad band of “medium” threats (i.e., scenario 2) does HSD provide additional needed Minuteman survivors. Even in that case, there are many technical difficulties facing HSD which might reduce its capabilities and thereby reduce the number of additional survivors below 100.[Page 680]
- —The Soviets might develop RVs (e.g., maneuvering RVs) or special endo-atmospheric penaids which would require more interceptors per RV, thus more quickly exhausting the interceptor inventory.
- —The Soviets could also time a barrage attack of hundreds or even thousands of RVs to arrive at the defended ICBM field over a very short period of time (e.g., 10–20 seconds). This would put tremendous demands on the computer software of the tracking radars which must track all the RVs, discriminate them from penaids, and guide the interceptors to the target. Moreover, the detonation of interceptors might black out the radars, destroy other interceptors which had not yet reached their targets, etc.
on the other hand, unless the technical defects of the HSD were very evident, the Soviet planner might hesitate to rely on any possible weakness and feel he must rely on the simple (and expensive) tactic of exhausting our interceptors with an equivalent number of attacking RVs.
Assuming that an additional 100 Minuteman were saved, there is still some question of the strategic significance of this incremental number of survivors.
- —If Minuteman alone were used to retaliate against the Soviets, 100 more Minuteman could account for about 5–8% more Soviet fatalities. (Against zero or NCA ABM, 100 Minuteman account for about 15% fatalities, 200 for about 20% and 300 for about 25%.)
- —However, we presumably would also have some surviving bombers and SLBMs. Assuming medium range (i.e., scenario 2) threats against these other forces and say 50 to 200 surviving Minuteman even without HSD, the addition of 100 more Minuteman survivors would increase Soviet fatalities by about 1–5%. (12 surviving SSBNs out of the 31 normally in-transit or on-station can inflict 25–28% fatalities against zero or NCAABM. Adding some bombers and some Minuteman which survive even without HSD pushes fatalities and targets covered to a level where additional warheads provide diminishing returns.)
- —As for U.S. attacks against other than urban/industrial targets, the scenario where HSD is effective (i.e., scenario 2 medium range threats) has about 100 or more Minuteman survivors even without HSD. Moreover, the Poseidon SLBMs would also be effective against most of these other targets.
2. The Soviet Deployment
Allowing HSD to the Soviets at one ICBM field provides them with some strategic benefits. The ICBMs at that field would obtain substantial protection. (Note, though, that the largest Soviet ICBM field has about 130 ICBMs and this is west of the Urals. The largest east of the Urals has 77 ICBMs and the largest SS–9 field has 65 missiles.)
- —The radars at the ICBM field could be used as a base for a broad regional defense upon abrogation of the agreement.
- —Because of verification difficulties, the Soviets could, by cheating which we are unlikely to detect, acquire a substantial exoatmospheric intercept capability at ranges greater than 300 nm.
However, if the ICBM field is east of the Urals, the sparse population there means that the collateral population protection is limited. No more than 12% of the total Soviet population is within 400 nm of any one ICBM field.
- —If the Soviets insist on protection of more than one ICBM field, then population protection grows. About 23% of the Soviet urban population is within 400 nm radius of five ICBM fields with a total of 150 silos west of the Urals.
- —If the Soviets resist any geographical restrictions and also insist on being able to protect 150 silos, then they could defend up to 45% of their urban population.
- Source: National Archives, Nixon Presidential Materials, NSC Files, NSC Institutional Files (H-Files), Box H–010, Verification Panel Meeting SALT Cancelled 1/27/72. Top Secret; Sensitive. Sent for urgent information.↩
- See Documents 216 and 225.↩
- NIE 11–8–71, October 21, 1971, entitled “Soviet Forces for Intercontinental Attack,” is printed in Foreign Relations, 1969–1976, volume XXXIV, National Security Policy, 1969–1972, Document 198.↩