97. National Security Decision Memorandum 731


  • The Members of the National Security Council
  • The Attorney General
  • The Director, Arms Control and Disarmament Agency
  • The Director of Central Intelligence


  • Supplemental Guidance for Strategic Arms Limitation Talks

After considering the Delegation’s request for changes in NSDM 692 and the views of the Verification Panel, the President has directed that the following supplemental guidance be issued:

The limit in paragraph 2(B) of NSDM 69 would entitle the United States as well as the USSR to 250 launchers for modern, large missiles (i.e., missiles with a volume in excess of 70 cubic meters and of a type which first became operational in 1964 or later), within the overall limit on strategic nuclear delivery vehicles and the sub-limit on launchers for ICBMs and sea-based missiles. The force permitted each side by paragraph 2(B) could be obtained by retention of existing launchers already associated with modern, large missiles, by retrofitting such missiles into existing launchers not hitherto associated with such missiles, by basing such missiles on sea-borne platforms, or by building new silos for them.
The limits set forth in paragraph 2(E) and (F) on relocation of existing ICBM silos, modification of existing ICBM silos in externally observable ways, on construction of new silos for IR/MRBMs, and on construction of all new ICBM silos are particularly intended to enhance confidence in verification by national means of the limit of paragraph 2(B). (In conjunction with the ban on land mobile ballistic missiles set forth in paragraph 2(F), they are also important for verification of the overall limit on strategic nuclear delivery vehicles and the sub-limit on missiles.) These limits would be interpreted to mean that any silo whose construction was initiated after an agreed date would be counted against the paragraph 2(B) limit. Similarly, any externally observable [Page 321] modification of existing silos would require that the modified silos be counted against that limit. The Delegation is to explain that these provisions are required because, while we do not wish to interfere unnecessarily with the flexibility of each side to determine its own force mix, we regard it as essential that there be a verifiable and effective limit on modern, large missiles. We believe we could not by national means verify confidently that a new silo had not been designed so as to be able to launch very large missiles or that a silo modification did not have the purpose of enabling the silo to accommodate such missiles. Therefore, we must insist that any new or modified silos be counted as if they contained modern, large missiles.
Obtaining a separate limitation on modern, large missiles and assuring that such a limitation is adequately verifiable are absolutely essential. Preservation of particular possible means of building a U.S. force of modern, large missiles must not interfere with obtaining an effective and verifiable limit on the Soviet force of such missiles. This priority must be borne in mind in discussing with the Soviets the U.S. proposals with respect to offensive forces and in evaluating any possible modifications of the U.S. position.
The privilege of substituting among bombers, ICBMs and sea-based missiles set forth in paragraph 2(D) of NSDM 69 would be subject to the collateral and subsidiary constraints set forth in the subsequent paragraphs of the NSDM (and amplified above) as well as to the various numerical limits. The Delegation may, if it thinks it advisable, describe the United States proposal as allowing “expanded” freedom-to-mix or “full freedom-to-mix, subject to stated conditions.”
It is recognized that the Soviets may not accept all of the collateral constraints on offensive systems set forth in NSDM 69 and that they may object to other provisions as well. However, possible changes in the U.S. position will be considered in the context of concrete situations and proposals as they arise through the negotiating process and in the light of possible Soviet counter-concessions.

Henry A. Kissinger
  1. Source: National Archives, Nixon Presidential Materials, NSC Files, NSC Institutional Files (H-Files), Box H–208, National Security Decision Memoranda, NSDMs 51–100. Top Secret. Copies were sent to the Chairman of the Joint Chiefs of Staff and the senior members of the U.S. SALT Delegation.
  2. Document 94.