Foreign Relations of the United States, 1964–1968, Volume XI, Arms Control and Disarmament

111. Memorandum From the Joint Chiefs of Staff to Secretary of Defense McNamara¹

JCSM-37-66

Washington, January 15, 1966.

SUBJECT

• Comprehensive Test Ban Treaty (U)

1. (S) In response to an oral request from the Assistant Secretary of Defense (ISA) on 6 January 1966, the views of the Joint Chiefs of Staff are provided on the position paper in the Appendix hereto, prepared by the Director, US Arms Control and Disarmament Agency (ACDA).² This paper recommends that the United States press for a Comprehensive Test Ban Treaty (CTBT) at the Eighteen-Nation Disarmament Conference (ENDC) when it reconvenes on 27 January 1966.

2. (S) A study by the Joint Chiefs of Staff on the Military Implications of a Comprehensive Nuclear Test Ban Treaty was forwarded by JCSM-348-65, dated 11 May 1965, subject: “Analysis of Comprehensive Test Ban (U).”³ Views of the Joint Chiefs of Staff on ACDA proposals for a comprehensive test ban and threshold ban were forwarded by JCSM-601-65, dated 5 August 1965, subject: “Nuclear Test Ban Proposals (U).”⁴ These views of the Joint Chiefs of Staff remain valid and are relevant to the current ACDA position paper.

3. (S) The ACDA paper proposes that at the resumption of the ENDC on 27 January 1966, the United States attempt to negotiate a CTBT, providing for an unspecified number of on-site inspections. The number of inspections would be subject to negotiation but would have to be sufficient to give confidence that the treaty was being observed. On-site inspections would be conducted in accordance with a modalities paper prepared by ACDA. In the event that the USSR were unwilling to permit the on-site verification necessary for a CTBT, the United States would then propose an extension of the present Limited Test Ban Treaty (LTBT) to underground tests with a seismic signal of 4.75 or higher without inspections.

4. (U) The views of the Joint Chiefs of Staff on a Threshold Test Ban (TTB) have been provided by JCSM-28-66, dated 13 January 1966, subject: “Test Ban Proposals (U).”⁵ The ACDA memorandum states that a modalities paper for on-site inspection will be circulated for comment at staff level. This paper has not been referred to the Joint Chiefs of Staff, and it is emphasized that the Joint Chiefs of Staff desire to make recommendations on any on-site inspection procedure prior to it being discussed, in public or in private, with foreign governments.

5. (TS) There are serious gaps in hard US intelligence about the state of Soviet research in the newest weapon effects areas known to US scientists. However, there are indications that the USSR already may have made important gains in nuclear weapons technology beyond US capabilities, which could alter the military balance. Such gains may have occurred in their knowledge of weapon effects causing communications and radar blackout; they also may include advances in the area of enhanced gamma, cold, and hot X-rays for antiballistic missile (ABM) and offensive applications. This technology may introduce important vulnerabilities in the US strategic missile systems.

6. (TS) It is believed that the Soviets have begun to deploy an ABM defense; however, it has not yet been determined whether the defense will be an area or terminal system, or a combination of both. USSR deployment of an ABM system capitalizing on advanced nuclear technology (which the Soviets may possess), combined with improvements in strategic weapon design and potential counterforce actions which exploit US vulnerabilities, could upset the nuclear balance in favor of the USSR. To counter this threat, the United States must develop its own ABM system, must remove known vulnerabilities in US strategic missile systems, and must develop an advanced reentry system. These developments require vigorous nuclear testing which can be accomplished within LTBT restrictions.

7. (TS) It is important, from the standpoint of ability to monitor a CTBT, to assess whether there is a minimum yield below which crucial military gains could not occur through clandestine testing. [3-1/2 lines of source text are not declassified] Vigorous exploitation of low yield (less than 1 KT) techniques as a sole means of weapons development, if successful, could lead to important technical gains conceivably capable of changing the nuclear balance. As a practical matter, the yield below which crucial military gains could not occur through nuclear testing is unknown.

8. (S) The current US Atomic Energy Detection System can, with acceptable confidence, detect nuclear explosions in most environments at thresholds of approximately 10 KT in the Northern Hemisphere and as high as 100 KT in the Southern Hemisphere. If current improvement plans prove out, a reasonable capability can be expected in 2 to 3 years to detect signals from a 5 KT nuclear test in almost all environments in the Northern Hemisphere and 60 KT in the Southern Hemisphere. Testing below these levels may go undetected, and, with decoupling and evasion techniques, tests well above these yields may also go undetected.

9. (TS) In summary, the Joint Chiefs of Staff oppose a CTBT as not in the security interest of the United States. The United States must approach any nuclear test ban from a position of strength. Although it may be accepted that the United States enjoys a favorable strategic position, this advantage is threatened by the probable deployment of a Soviet ABM system and the important advances that the Soviets have probably made in weapons effects technology. To counter this threat, the United States must develop its own ABM system and must remove vulnerabilities in US strategic missile systems. To realize these goals, substantial underground testing is required. Additionally, verification procedures in being and projected are insufficient to insure that under a CTBT the USSR could not conduct sufficient tests to achieve important advances in nuclear technology. The Joint Chiefs of Staff desire to make recommendations on proposed on-site inspection procedures prior to their being discussed, in public or in private, with foreign governments.

For the Joint Chiefs of Staff:

Earle G. Wheeler ⁶
Chairman Joint Chiefs of Staff

1. Source: Johnson Library, National Security File, Subject File, U.S. Draft Nonproliferation Treaty, Box 27. Top Secret, Restricted Data.
2. Not printed.
3. Not found.
4. See footnote 5, Document 109.
5. Document 109.
6. Printed from a copy that indicates Wheeler signed the original.