112. Memorandum From Secretary of Defense McNamara to the Chairman of the Joint Chiefs of Staff (Wheeler)1


  • Minuteman Force Posture (U)

In my draft memorandum for the President on Strategic Offensive and Defensive Nuclear Forces, dated October 16, 1965,2 the planning figures of 700 Minuteman II and 300 Minuteman III were used. These figures were based on an extrapolation to 1970 of the present Soviet target system and the present philosophy that underlies the US Single Integrated Operations Plan (SIOP). The calculations that lead to these figures take proper account of other programmed U.S. strategic forces in the same time period, e.g., the Polaris force. However, no account has yet been taken in these calculations of the implications of possible Soviet anti-ballistic missile (ABM) defenses.

The immediate questions that should be answered this year are: [Page 340]

What is a proper mix of Minuteman II and Minuteman III missiles, and hence how may Mk 12 and MK 17 re-entry vehicles should be procured for use on Minuteman missiles?
How should penetration aids to accompany Mk 12 re-entry vehicles be distributed through the Minuteman III force, against various possible Soviet ABM threats?

Clearly, these are complex questions. Overall U.S missile force postures will depend on the types of Soviet ABMs we assume. The distribution of Minuteman II/Minuteman III will depend on the Polaris/Poseidon mix, and will be affected by possible development and eventual deployment of a small re-entry vehicle of the Mk 100 type for Minuteman. Perhaps most importantly, the desirable mix of Minuteman II/Minuteman III will depend on the strategic objectives we assign to the U.S. offensive forces, as reflected in the type of SIOP assumed to govern the use of these forces in the time periods and environments of interest.

In addition to providing very important source material for rather near-term Minuteman force posture decisions, I expect that a study of these questions would be of significant aid in a number of other areas:

Strategic Operations against ABMs, including use of TAPS and other elements of a Minuteman control system.
Design of MIRVs that might have to be used against hard targets as well as against defended cities.
Compatibility of Assured Destruction and of Damage Limiting criteria in designing force postures that include MIRVs and that must penetrate ABMs.

I should like you to perform such a study in stages. The first stage will be to consider the types of SIOP, and hence the type of SIOP guidance, that might seem appropriate for the employment of U.S. missile forces against a Soviet target list protected by ABM defenses. To be specific, I suggest you consider SIOP guidance for the programmed U.S. forces at end FY 1971, against National Intelligence Estimates of Soviet strategic offensive forces and two Soviet ABM threats:

An ABM deployment consisting of some 1,000 area interceptors;
An ABM deployment consisting of some 1,000 area interceptors plus 1,000 terminal interceptors, deployed at the 25 largest Soviet cities in rough proportion to their population.

The second stage will be to carry out two calculations:

A simple, pilot analysis of the performance of the programmed force, against the particular ABM threat and in the face of a specific Soviet attack. The programmed force would be operated under the SIOP guidance resulting from Stage I of the study.
An Assured Destruction calculation to measure the number of fatalities that could be inflicted by this U.S. force against the same [Page 341]Soviet threat if the entire U.S. force were applied to Soviet urban-industrial targets.

After my review of the results of the first two stages, I would like to specify a small number of alternative combinations of U.S. force postures, Soviet offensive threats and ABMs, and scenarios. For each such combination, an evaluation of both the Damage-Limiting capability and of the Assured-Destruction capability of each U.S. posture will be requested.

I would like to receive the SIOP guidance requested above, together with the rationale behind it, by February 15, 1966. This discussion may assume a good knowledge of the present SIOP on the part of my staff. It should discuss how a SIOP in the face of an ABM would differ from our present plan. It can be in outline form, but it should be complete enough to allow a simulated laydown of arbitrary mixes of the U.S. strategic weapons available in 1971, against a Soviet target list of the size and structure that might be predicted for that time on the basis of National Intelligence Estimates. For this purpose, details of the assumed Soviet SBM are not highly relevant. Much more important are questions of targeting philosophy, such as, for instance, the desirability of attacking ABM radars as part of a counter-military task, and the desirability of choosing urban-industrial targets on a rank-order basis, instead of on a basis of maximum total fatalities.

Robert S. McNamara 3
  1. Source: Washington National Records Center, OSD Files: FRC 330 70 A 4443, 381 SRF 1966. Secret. Drafted by Ike Selin (OASD(SA)SP) on January 3 and rewritten by F.S. Hoffman on January 12. An attached January 21 covering memorandum from Enthoven to McNamara further explains the purpose of the studies proposed in the memorandum and recommends McNamara’s signature.
  2. Not found; for text of the November 1, 1965, draft memorandum, see Document 103.
  3. Printed from a copy that indicates McNamara signed the original.