At a time when U.S.-Russian relations continue to deteriorate, it is useful to recall how the United States and the Soviet Union found common ground during the Cold War on one vital national security issue—nuclear nonproliferation. An important, but by no means singular, case of nonproliferation cooperation between Washington and Moscow occurred in the 1970s when the two countries were military and ideological adversaries. Although the circumstances prompting superpower action to prevent a South African nuclear test in the Kalahari Desert in 1977 were unusual, careful examination of the case suggests a number of lessons that are relevant today.
Some of the specifics of the South African case remain hazy, but a large body of evidence supports the conclusion that the United States and the Soviet Union collaborated in a sustained, multi-faceted, and successful fashion to prevent South Africa from undertaking a nuclear test in the Kalahari Desert in 1977.  The achievement, ultimately, did not preclude South Africa’s acquisition of nuclear weapons, but it did demonstrate the readiness of two Cold War adversaries to work together in pursuit of a common nonproliferation goal.
During the late 1970s, the United States and the Soviet Union adopted a cooperative approach to prevent the South African nuclear test despite fierce East-West competition and conflict in the Horn of Africa, including military intervention by Soviet allies. This cooperation also took place at a time when nuclear negotiations between the superpowers were temporarily stalled; it was shortly after the Committee on the Present Danger issued a harsh warning on the dangers posed by the Soviet nuclear menace, and while the Carter administration was enunciating its commitment to making human rights an important aspect of U.S. foreign policy. However, nonproliferation concerns appeared to trump other foreign policy considerations, a stance possibly made easier by the international norm enshrined in the relatively new Treaty on the Non-Proliferation of Nuclear Weapons (NPT).
The South African case also is interesting in terms of the readiness of the superpowers to share sensitive intelligence information. For the Soviet Union, this was particularly noteworthy as it probably risked compromising a Soviet spy in South Africa. The traditional version of events has been that the Soviet Union discovered South Africa's nuclear test site in the Kalahari, and informed the United States of its existence a few weeks after a Soviet reconnaissance satellite passed over the site on July 3 and 4, 1977. Soviet officials do not appear to have acknowledged any information other than that gained by national technical means, but it is likely there was U.S. speculation about Soviet motivations for satellite reconnaissance over the precise portion of the Kalahari Desert where two test shafts were dug.  However, there was a readiness to discuss intelligence information with their U.S. interlocutors, which almost certainly was facilitated by the already well-established experience of U.S.-Soviet cooperation under SALT 1 and at fora such as the London Suppliers Group (predecessor to the Nuclear Suppliers Group), the International Atomic Energy Agency, and the NPT review process.
Finally, the 1977 case suggests that behind the scenes diplomacy on nonproliferation can prevail even when public rhetoric may point in the opposite direction. Although the Soviet press accused the United States and its Western allies of abetting South Africa’s nuclear weapons aspirations, senior Soviet officials concurrently worked closely behind the scenes with their U.S. counterparts. And in the UN General Assembly, Moscow demonstrated considerable restraint in how it depicted U.S. nuclear assistance to South Africa, leading U.S. Ambassador to the United Nations James Leonard to characterize Soviet Foreign Minister Andrei Gromyko’s commentary on the topic as “careful and moderate.”  By the same token, Washington was prepared to accept fallout from its strong stance against South African testing even if it might damage its foreign policy objectives toward other states in southern Africa, including Rhodesia and Namibia. Both superpowers took risks to cooperate because of a convergence of threat perceptions related to nuclear proliferation.
But how unique was this form of cooperation during the Cold War? The South African case was actually part of a much larger universe of U.S.-Soviet cooperative nonproliferation activities during the period. The best-known example of this cooperation was the negotiation of the NPT, which was concluded in 1968. However, the cooperation actually became more routine and extensive in 1974 following India’s so-called “peaceful nuclear explosion.” The Indian test was an eye-opening nonproliferation learning experience for U.S. decision makers, and in some ways paralleled the lessons learned earlier in Moscow after China exploited Soviet nuclear assistance to develop its own nuclear weapons.
U.S.-Soviet cooperation found expression in efforts to tighten nuclear export controls and to gain greater adherence to the NPT. For example, at meetings of the London Suppliers Group, the Soviet Union regularly aligned itself with the proponents of stringent nuclear exports, a situation that usually led Moscow and Washington to join forces more frequently than did the United States and a number of its Western allies such as France, West Germany, and Japan. Similarly, it was typical for the U.S. and Soviet delegations to work together at meetings of the International Atomic Energy Agency and during the NPT review process. Significantly, this consultation and cooperation continued across both U.S. Democratic and Republican administrations and even survived the Soviet invasion of Afghanistan in 1979. Indeed, during much of the Carter and Reagan presidencies, high-level bilateral consultations between the U.S. and Soviet Union on a broad range of nonproliferation issues were held every six months. 
U.S. and Russian leaders would do well to recall how their countries were able to put aside major policy differences at various points during the Cold War, including nearly 40 years ago to strengthen the recently negotiated NPT by working jointly to prevent a South African nuclear test. Such cooperation remains even more vital today, and should be possible to sustain as U.S. and Russian interests largely coincide in at least this one important national security domain.
 This essay's short account of Soviet-U.S. cooperation to prevent a nuclear weapons test by South Africa omits a number of important details, which are described in a forthcoming study by the authors. The Kalahari case study is part of a larger set of cases involving U.S.-Soviet/Russian cooperation on nonproliferation being studied by the Center for Nonproliferation Studies under grants provided by the MacArthur Foundation. The authors wish to thank Jeffrey Lewis and Sam Meyer for their help with this piece.
 The authors are part of a team at the Center for Nonproliferation Studies undertaking a series of historical case studies in order to better understand the drivers of past U.S.-Soviet/U.S.-Russian cooperation and the obstacles that had to be overcome. This research is supported by the MacArthur Foundation.
 Recent interviews by the Center for Nonproliferation Studies (CNS), and declassified documents raise new questions about precisely when and how the United States learned of the Kalahari test site. Declassified documents indicate that the first images of the test site by the United States were taken on July 4, well before the Soviets informed the United States on August 6. CNS is currently examining when the U.S. actually analyzed the photos and what prompted it to focus on the site at the same time as the Soviet Union.
 See the statement by Foreign Minister Gromyko reported in: United Nations General Assembly, Thirty-Second Session, 8th Plenary Meeting, Tuesday, September 27, 1977, A/32/PV.8; and the conversation by Ambassador Leonard with Ambassador Viktor Issraelyan reported in U.S. Department of State declassified document REF: USUN3566.
 For more on these interactions see William C. Potter, "Nuclear Proliferation: U.S.-Soviet Cooperation," The Washington Quarterly (Winter 1985), pp. 142-143.
* Slide Cover Image: "Kalahari in Namibia,” Elmar Thiel via WikiMedia Commons.
 See Jean du Preez and Thomas Maettig, “From Pariah to Nuclear Poster Boy,” in William C. Potter with Gaukhar Mukhatzhanova, eds., Forecasting Nuclear Proliferation in the 21st Century: A Comparative Perspective, Vol 2 (Stanford, CA: Stanford University Press, 2010), p. 309.
 Helen Purkitt and Stephen Franklin Burgess, South Africa’s Weapons of Mass Destruction, (Bloomington: Indiana University Press, 2005), p. 38.
 Waldo Stumpf, “Birth and Death of the South African Nuclear Weapons Programme," Conference Presentation, 50 Years After Hiroshima, Castiglioncello, Italy, September 28 - October 2, 1995, https://fas.org.
 Nic von Wielligh, The Bomb: South Africa’s Nuclear Weapons Programme (Pretoria: Litera Publications, 2015), pp. 136-137.
 David Albright, Paul Brannan, Zachary Laporte, Katherine Tajer, and Christina Walrond, “Rendering Useless South Africa’s Nuclear Test Shafts in the Kalahari Desert,” Institute for Science and International Security, November 30, 2011, https://isis-online.org.
 Jeffrey Lewis, "Geolocating the Kalahari Test Site," Arms Control Wonk, May 21, 2015, www.armscontrolwonk.com.
 Nic von Wielligh, The Bomb: South Africa’s Nuclear Weapons Programme (Pretoria: Litera Publications, 2015), p. 143; Jeffrey Richelson, Spying on the Bomb: American Nuclear Intelligence from Nazi Germany to Iran (New York: WW Norton, 2007). p. 278.
 Richelson, Spying on the Bomb, pp. 277-282.
 Electronic telegram, “Soviet Demarche on South African Nuclear Program,” August 11, 1977; Central Foreign Policy Files, created 7/1/1973-12/31/1979, documenting the period 1973-12/31/1979 [Electronic Record]; General Records of the Department of State, Record Group 59; National Archives at College Park, College Park, MD [retrieved from the Access to Archival Databases at www.archives.gov, September 19, 2016], https://aad.archives.gov.
 "Letter, Warren Christopher to William Hyland, 'Response to Soviet Message on South Africa'," August 10, 1977, History and Public Policy Program Digital Archive, National Archives, Record Group 59, Department of State Records, Records of Warren Christopher, box 16, Memos to White House 1977. Obtained and contributed by William Burr for NPIHP Research Update No. 25, https://digitalarchive.wilsoncenter.org.
 Nic von Wielligh, The Bomb: South Africa’s Nuclear Weapons Programme (Pretoria: Litera Publications), 2015, p. 137; Richelson, Spying on the Bomb, 279.
 Richard Van Der Walt, Hannes Steyn, and Jan Van Loggerenberg, Armament and Disarmament: South Africa’s Nuclear Experience, (Lincoln, NE: iUniverse, 2005), p. 40-41.
 Murrey Marder, “Carter Says S. Africa Denies Intent to Develop Any Nuclear Explosives; Carter Reaffirms Faith in His Budget Director, Reaffirms His Faith in Budget Director,” The Washington Post, August 24, 1977; President Jimmy Carter, “The President’s News Conference,” August 23, 1977, www.presidency.ucsb.edu.
 Anna-Mart van Wyk and Jackie Grobler, “The Carter Administration and the Institution of the 1977 Mandatory Arms Embargo against South Africa: Rhetoric or Active Action?” Historia, Vol. 51, Issue 1, May 2006, p. 183.
 Electronic telegram, “Contingency Statement on South African Nuclear Program for Lagos Conference” August 20, 1977, Central Foreign Policy Files, created 7/1/1973-12/31/1979, documenting the period 1973-12/31/1979 [Electronic Record]; General Records of the Department of State, Record Group 59; National Archives at College Park, College Park, MD [retrieved from the Access to Archival Databases at www.archives.gov, September 19, 2016], https://aad.archives.gov.