Kissinger weighed nuclear test ban against Soviet cheating
By Eleanor Voss ·
Top officials feared the USSR would use a test ban as a cloak for secret nuclear progress, potentially leapfrogging U.S. capabilities while Americans adhered to a quota.
On June 4, 1971, Henry A. Kissinger issued National Security Study Memorandum 128. It was a directive of the highest sensitivity, marked Top Secret, and addressed to the Secretary of State, the Secretary of Defense, the Director of Central Intelligence, and the Director of the Arms Control and Disarmament Agency.
The document, found in the Foreign Relations of the United States (State Dept) archive, records a presidential order to review United States policy regarding underground nuclear testing. The administration was not looking for a simple yes or no on a ban; it requested an evaluation of four distinct paths: a comprehensive test ban, a threshold test ban, a quota test ban, and a moratorium.
By 1971, the world had already lived under the Partial Test Ban Treaty for eight years. According to the public record, that 1963 treaty prohibited detonations in the atmosphere, outer space, and underwater, leaving the underground environment as the only legal venue for the nuclear laboratories to refine their arsenals. NSSM 128 suggests that by the early 1970s, the Nixon administration was questioning whether that remaining loophole should be closed and how the U.S. could ensure the Soviets didn't use a ban as a cloak for secret progress.
Seismic systems
The first priority of the review was "Verification possibilities." For a physicist, this is where the memo becomes concrete. The administration wanted to know if the U.S. could actually trust its ears. The directive calls for an analysis of the "estimated capabilities of present, currently planned and possible future seismic systems," as well as a hard look at the "history of past system performance versus expectations."
Seismology is the primary tool for monitoring underground tests; a nuclear explosion creates a distinct seismic signature compared to an earthquake. However, the memo acknowledges that these systems might not be enough. Kissinger asks for an evaluation of the "added capabilities provided by on-site inspection or on-site automatic seismic stations." The tension here is clear: a treaty is only as strong as the ability to prove it is being followed. If the seismic data remained ambiguous, the U.S. would have to rely on boots on the ground or automated sensors in foreign territory—both of which carry immense diplomatic and intelligence risks.
Soviet clandestine testing
The second and third areas of analysis deal with the raw physics of the arms race. The administration requested a study on the effects of a ban on U.S. weapons development, specifically how it would impact "meeting current and anticipated weapons needs and requirements" and the potential for "conversion programs" for the laboratories.
Equally critical was the "Estimated effects on Soviet weapons development." The specific fear cited in the memorandum is "potential gains from clandestine testing." The worry was that a ban would not stop Soviet research but would simply drive it deeper underground or into more secretive channels, potentially allowing the USSR to leapfrog U.S. capabilities while the Americans adhered to a quota or a moratorium. This is the classic security dilemma: the desire for arms control tempered by the fear that the opponent will cheat with impunity.
Plowshare applications
Beyond the warheads, the memorandum addresses a peculiar ambition of the era: the Peaceful Nuclear Explosion (PNE) programs. Kissinger asks for an analysis of the "domestic and international consequences of restricting or prohibiting such explosions," specifically mentioning "ways of accommodating Plowshare applications."
Project Plowshare was the U.S. government's attempt to find civilian uses for nuclear detonations, such as carving out harbors or creating canals. The memo recognizes a dual-risk here. First, restricting PNEs might stifle perceived economic or scientific utility. Second, and more pragmatically, there was the concern regarding "the possibilities of utilizing PNE’s for evasion of a test ban." In other words, if the Soviets claimed a clandestine blast was merely a "peaceful" excavation project, how would the U.S. prove otherwise?
The study was tasked to a Verification Panel that included a representative from the Atomic Energy Commission. The political stakes extended beyond the superpowers, as Kissinger sought an analysis of the effects on "U.S. relations with allied nuclear powers" and the broader goal of "controlling further proliferation of nuclear weapons."
Copies of the memorandum were sent to David, Seaborg, and Moorer. The administration set a tight deadline for the results: the study was to be ready for the National Security Council's consideration by August 15, 1971. Whether the subsequent analysis convinced the President to move toward a threshold or a comprehensive ban remains a question for the files that followed this directive.