70. Memorandum From the President’s Special Assistant for National Security Affairs (Bundy) to President Johnson1


  • A further message to the Soviets on their nuclear test that vented2
As you know, we picked up radioactive debris from a Soviet test that vented on January 15, 1965. We reported this fact to the Soviet Union and asked for an explanation.
Ambassador Dobrynin came back with an oral statement in which the Soviet Government agreed that there had been venting, but denied the possibility of fallout outside the limits of the Soviet Union. Meanwhile, we got pictures of the crater, and we have been refining our analysis of the Soviet test. It is now reasonably certain that the test was intended as a Plowshare excavation experiment. The explosion was very [Page 190] clean, with a yield of 300 to 400 kilotons. We believe that the venting was not accidental but was inherent in the cratering design of the experiment. On the other hand, the weather conditions at the time may well have led the Soviets to believe that there would be no fallout beyond the borders of the Soviet Union.
The test clearly raises a question of its legitimacy under the test ban treaty, and we face something of a dilemma. On the one hand, if we do not keep pressing the Soviets for a fuller explanation, we may seem to be giving our tacit approval to a violation. On the other hand, if we take a prosecutor’s attitude we may only succeed in pinning ourselves to a position of rigidity, on very small amounts of venting, that will work against our own interest at some later stage when we may wish to make similar tests of very clean devices of our own.
The conclusion that we have reached is that we should register our dissatisfaction with the existing Soviet position and ask for more information. This will protect us from seeming to accept an explanation that is simply not in accordance with the facts, while at the same time we avoid the position of a prosecutor under the treaty. Moreover, if by any chance the Soviets do provide additional information, it will help to strengthen the precedents for full disclosure of the facts surrounding any cases of venting in the future.
The Committee of Principals (State, Defense, AEC, JCS, CIA, Hornig, and Bundy) agree upon the Aide-Mémoire attached at Tab A, for presentation by Ambassador Thompson to Ambassador Dobrynin.3
McG. B.

Tab A4


The United States Government has studied Ambassador Dobrynin’s oral statement of January 25 together with all other presently available [Page 191] data on the Soviet Union underground explosion of January 15, 1965 in the light of the Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space and Under Water.

The United States has noted the observation contained in Ambassador Dobrynin’s oral statement that the quantity of radioactive debris that was placed in the atmosphere was “so insignificant that a possibility of its fall out outside the territorial limits of the Soviet Union is excluded.” However, we are unable to reconcile the scientific findings with respect to the radioactive debris resulting from the Soviet Union’s test with the observations in Ambassador Dobrynin’s oral statement.

On January 19, 20, 21 and 22 radioactive debris, which can be associated directly with the Soviet nuclear explosion on January 15, was collected outside the USSR. U.S. aircraft operating in the Sea of Japan acquired fresh fission fragments traceable to the Soviet test. In addition, the Radioactivity Countermeasures Headquarters of the Government of Japan has published data collected from many ground stations on January 20, 21 and 22 indicating concentrations of radioactive debris which were as much as 10 to 100 times the levels on previous days.

Article I (b) of the Treaty imposes an obligation on parties to prohibit, prevent and not to carry out any nuclear explosion in any environment including underground, “if such explosion causes radioactive debris to be present outside the territorial limits” of the party conducting the test.

In view of the foregoing, the Government of the United States requests further information concerning this event.

  1. Source: Johnson Library, National Security File, Subject File, Nuclear Testing—USSR, Vol. I, Box 31. Secret.
  2. Regarding discussions leading to the preparation of this message (aide-mémoire), see Document 69.
  3. The approved option at the end of the memorandum is checked.
  4. Confidential; Limdis.
  5. This aide-mémoire has not been found, but was later referred to as dated February 15. See footnote 7, Document 76. U.S.-Soviet discussions on this Soviet test apparently continued, for Seaborg later recounted: “On November 19, 1965, the State Department announced, ‘on the basis of discussions with the Soviet Government,’ that the venting from the Soviet test had been a result of ‘miscalculation’ and that the United States had asked the USSR ‘to take precautions to assure observance of the limited test ban treaty.’” (Stemming the Tide, p. 225)