239. Memorandum From John Marcum and Marshall Brement of the National Security Council Staff to the President’s Assistant for National Security Affairs (Brzezinski)1


  • Soviet Nuclear Test (S)

Jim Schlesinger has written you (Tab B)2 to point out that the most recent Soviet nuclear test has a high probability of having exceeded the 150 KT threshold and to urge that we seek an explanation of this event [Page 587] from the Soviets. This is technically correct, but the situation is actually less certain since other seismic data, which we do not understand fully, indicate that the yield may have been considerably smaller. Nevertheless, Schlesinger’s concerns are well founded and, per David’s instructions, the State Department delivered a démarche we had already initiated to the Soviets this afternoon (Tab C).3 (S)

At David’s suggestion, we also called in Bessmertnykh to reinforce State’s protest. We asked him whether or not, in light of the three large explosions this summer, the Soviets intended to adhere to the 150 kt limit and made clear that we were free to respond appropriately. Bessmertnykh reaffirmed strongly that the Soviets considered themselves bound by this limit and fished for an indication that we were more concerned about the domestic consequences than the actual yield of the explosion. We responded that it was the large size of this explosion and the earlier ones this summer that prompted our concern. (S)

We have prepared a brief response to Schlesinger at Tab A,4 informing him that you share his concerns and that the text has been protested to the Soviets. (S)


That you sign the memorandum at Tab A.

  1. Source: Carter Library, National Security Affairs, Brzezinski Material, Agency File, Box 8, Energy Department: 8–10/79. Secret. Outside the System.
  2. Document 238.
  3. Attached but not printed. That afternoon, Acting Assistant Secretary of State for European Affairs Goodby handed Soviet Chargé Vasev a démarche based on the draft at Tab C that noted the administration’s “concern” over the test. The text of the démarche is contained in telegram 227369 to Moscow, August 29. (National Archives, RG 59, Central Foreign Policy File, D790394–1013)
  4. Tab A is an August 24 memorandum from Brzezinski to Schlesinger which noted that the United States had “requested that they [the Soviets] provide technical data relating” to the test to which Schlesinger had alerted Brzezinski on August 22 [Document 238] as well as “the explosions of June 23 and August 3 which we had raised with them previously.” (Carter Library, National Security Affairs, Brzezinski Material, Agency File, Box 8, Energy Department: 8–10/79) Telegrams 166361 and 205927 to Moscow, June 28 and August 8 respectively, discuss the U.S. démarches to the Soviet Union concerning the June 23 and August 4 Soviet nuclear tests. (National Archives, RG 59, Central Foreign Policy File, D790292–0271 and D790358–1164 respectively)