Office of the Historian

131. Memorandum From the Department of Defense Representative on the Delegation to the Strategic Arms Limitation Talks (Nitze) to Director of Central Intelligence Helms1

Washington, February 2, 1971.

SUBJECT

  • Capability of the SS–11 Mod 2B Against Safeguard ABM Radars

Thank you for your memorandum of February 1 and its attachment;2 the attachment appears to answer the question I had intended.

My question apparently was not clearly expressed; I had no thought that the SS–11 triplets were independently targettable. What I meant to ask was whether or not each RV of the SS–11 triplets would not constitute a sufficient threat to the Safeguard radars (MSRs) at which a triplet was aimed to necessitate attempts to intercept each of the three RVs separately.3

If this is so, as it appears to be from paragraph 3 of your enclosure, then the potential number of RVs the Safeguard system (or an HSD system) might have to contend with could be the aggregate number of RVs on the SS–9s or follow on hard target threats, plus those on at least a percentage of the SS–11s.

With the current number of SS–11 silos operational or under construction, this would give an upper limit of perhaps 1700 RVs more than the threat projected with single RV SS–11s. If you assume that the Soviet Union would devote no more than fifty percent of his SS–11s to such a purpose, the numbers would, of course, be correspondingly reduced.

The inference could then be that the SS–11 triplets are designed not just to counter a potential area ABM, but specifically to counter an active defense of our land-based ICBMs.

Paul H. Nitze 4
  1. Source: Central Intelligence Agency, Executive Registry Files, Subject Files, Job 80–B01086A, Box 15, #469. Secret.↩
  2. Helms’s memorandum and its attachment are attached but not printed. In the memorandum, Helms stated: “My staff has considered your question whether the three warhead version of the SS–11 might be able to attack separate radars of the Safeguard system. They conclude from analysis of tests observed so far that the system does not have such a capability. This is because the warheads are not guided independently and because their impact points are separated by distances of less than two miles.” Helms’s attachment provided the technical data for the judgment.↩
  3. On February 5, R.J. Smith drafted for Helms a follow-up memorandum that was not sent. A typed note from Helms on the routing slip attached to the draft reads: “D/OSR, Nitze told me on the phone he is satisfied and does not want to perpetuate the exchange.” Both are attached but not printed.↩
  4. Printed from a copy that bears Nitze’s typed signature.↩