For a Hollywood blockbuster, Christopher Nolan’s Oppenheimer does an effective job of portraying the “father of the atomic bomb” as a complex, multifaceted human being, driven by a combination of arrogance and self-doubt and facing profound moral dilemmas. The movie—which debuts next month on most North American streaming platforms—alludes not just to the story of the race to build the bomb but also to the subsequent debate over whether to go beyond the development of fission weapons to create the “Super” or hydrogen bomb, based on nuclear fusion. J. Robert Oppenheimer famously opposed the H-bomb, partly on moral grounds. In his and the other critics’ view, its capacity for nearly unlimited explosive power rendered it useful only for mass murder of civilians. He also opposed it as a competitor to other uses of nuclear materials—then in short supply—for military purposes. But for all his moral concerns, Oppenheimer was not an antinuclear dove.
The movie hints at Oppenheimer’s concern—that the H-bomb project would divert resources from the fission-based nuclear weapons he preferred to build—but sometimes obscures it. Nolan’s Oppenheimer speaks vaguely of international control of atomic energy, yet the scientist’s efforts to promote such initiatives had failed by 1946. Asked how to respond to the first Soviet atomic test of August 1949, the movie’s Oppenheimer answers, “arms talks.” But the real Oppenheimer knew that negotiations by then were a lost cause, owing both to Soviet intransigence and US commitment to staying ahead in a nuclear arms race.
The movie doesn’t make clear enough the reality that Oppenheimer played a key role in the expansion of the US nuclear weapons program. Oppenheimer was particularly active during the early 1950s in the development of so-called tactical nuclear weapons (that is, weapons intended not to be dropped on cities but rather employed against targets of military relevance). That we worry today about Russian President Vladimir Putin’s threats to use nuclear weapons to alter the course of the war in Ukraine, and that the nuclear-armed North Atlantic Treaty Organization might respond in kind, owes much to Oppenheimer’s promotion of what became known as “nuclear plenty.”
In the wake of the atomic bombings of Hiroshima and Nagasaki, Oppenheimer initially shared the common view that the weapons’ only purpose was to inflict mass casualties on civilians by attacking cities. In May 1946, he wrote to President Harry Truman to oppose the planned series of tests of atomic weapons at the Bikini Atoll. Operation Crossroads, as it was called, was intended to test the effects of the weapons against naval vessels. Oppenheimer wrote, “surely the overwhelming effectiveness of atomic weapons lies in their use for the bombardment of cities and of centers of production and population.” He thought the study of the impact on naval forces by comparison “trivial” and a waste of money. Truman consulted Dean Acheson, then acting US State Secretary, about how to respond to this “letter from a ‘cry baby’ scientist,” the president’s standard epithet that found its way into Nolan’s movie.
Operation Crossroads went ahead anyway and coincided with the presentation at the United Nations by Bernard Baruch of the US plan for preventing a nuclear arms race. Based on the Acheson-Lilienthal Report, largely drafted by Oppenheimer, Baruch’s plan eliminated the provision for international control of uranium deposits and emphasized instead the punishment of countries that sought to use atomic energy for military purposes. Baruch insisted that the United States maintain its monopoly on nuclear weapons until intrusive inspection procedures had assured that no other countries possessed them—clearly a nonstarter for the secretive Soviet Union.
Oppenheimer was disappointed at the failure of international negotiations to control the bomb but was still eager to maintain his privileged access to policy circles in Washington. He devoted his attention to accelerating US production of fissile material and developing bomb designs that would use it more efficiently. As chair of the General Advisory Committee of the Atomic Energy Commission (AEC), he oversaw three major expansions of atomic production facilities in 1949, 1950, and 1952. The Sandstone series of nuclear tests in April and May 1948—a follow up of the 1946 Operation Crossroads—had demonstrated the success of new designs of smaller, more efficient nuclear weapons than had previously been available. At this point, US strategy for a potential war with the Soviet Union—including a feared invasion of western Europe—focused entirely on attacking Soviet cities with atomic weapons. But Oppenheimer preferred that nuclear weapons play a more direct role in defense. He chaired a panel on “long-range objectives” for the Pentagon’s Research and Development Board that recommended in August 1948 that nuclear weapons be developed for use on a battlefield. Norris Bradbury, Oppenheimer’s chosen successor as director of the Los Alamos Laboratory, accordingly, submitted a request in October “that a complete small weapon be readied for test early in 1951.” He relayed an order to the Sandia Laboratory, responsible for the weaponization of nuclear devices. Sandia was already at work on the “Mark 4” bomb, which consisted of an improved version of the Mark 3 “Fat Man” bomb dropped on Nagasaki. The Mark 4 was the first US atomic weapon to go into mass production and eventually came in a variety of yields, including one kiloton (1,000 tons of TNT equivalent), considered at the time small enough to use for tactical purposes.
In 1949, following the shock of the first Soviet nuclear test, Oppenheimer redoubled his efforts to promote tactical uses for atomic weapons. He opposed the crash program to develop the hydrogen bomb promoted by Edward Teller and Lewis Strauss, then-chair of the AEC, in favor of “bringing the battle back to the battlefield.” The October 1949 report of the AEC’s General Advisory Committee, where Oppenheimer and his colleagues came out against the Super, included a section on “tactical delivery.” The committee recommended to the AEC “an intensification of efforts to make atomic weapons available for tactical purposes, and to give attention to the problem of integration of bomb and carrier design in this field.” Some of what we know about Oppenheimer’s promotion of tactical nuclear weapons comes from the transcript of the 1954 hearings that feature in Nolan’s movie. Although Oppenheimer barely touches on this aspect, much of the hearing consisted of the efforts of the Manhattan Project leader and his allies to emphasize how much Oppenheimer had contributed to the postwar atomic arsenal.
Oppenheimer found an ally in US Army Gen. James Gavin, a member of the Pentagon’s Weapons Systems Evaluation Group. He served along with Adm. William Parsons—a close friend of Katherine and Robert Oppenheimer and their wartime neighbor at Los Alamos. Through Gavin’s work at the Pentagon, he had “become convinced that nuclear weapons had a tremendous field for tactical application, in fact, in the long run, probably the most promising field of all.” Oppenheimer’s promotion of such tactical applications put the proponents of the larger H-bomb on the defensive—to the point where they started singing the praises of hydrogen bombs for battlefield use. AEC chair Strauss, for example, wrote to President Harry Truman in November 1949 that “unlike the atomic bomb, which has certain limitations, the proposed [hydrogen] weapon may be tactically employed against a mobilized army over the area of the size ordinarily occupied by such a force.”
Oppenheimer had made it possible for the United States to pursue both fission and fusion weapons for any possible use by securing the expansion of production of atomic materials and advocating more efficient weapons. But if Oppenheimer thought he could defeat the Super by promoting tactical nuclear weapons, he was quickly disappointed. His fellow enthusiasts for battlefield nuclear weapons, including General Gavin, came out in favor of the H-bomb.
When the Korean War broke out in June 1950, Gavin worked with Gen. Kenneth Nichols to urge the Army’s chief of staff to recommend to President Truman “that we use nuclear weapons against the North Korean forces.” Nichols is familiar to viewers of Oppenheimer for his role during the Manhattan Project and later, as general manager of the AEC, for his effort to remove Oppenheimer’s security clearance in 1954. (We glimpse on screen his letter presenting the charges against Oppenheimer when Strauss hands it to the scientist.) Nichols and Gavin both believed, in the latter’s words, that “the situation in the summer of 1950 offered us a number of well worth-while tactical nuclear targets if we had had the moral courage to make the decision to use them.”
Oppenheimer made his views on the tactical use of nuclear weapons public in a speech to the New York Bar Association in January 1951. The Bulletin of the Atomic Scientists published an excerpt from Oppenheimer’s address in its next issue. Given “the extent of our investment in the atomic field,” Oppenheimer argued, “we cannot ignore what the atom can do for military purposes.” He then asked the question of using or not the atomic bomb. The Korean War, he said, had raised the issue of “atomic weapons in warfare” and “their use against military targets.” In his address, Oppenheimer declared that atomic weapons “are an integral part of military operations,” but should be used “only as adjuncts in a military campaign, which has some other components, and whose purpose is military victory.”
Although Oppenheimer seemed to favor the use of tactical nuclear weapons in a future war, his remarks were sufficiently ambiguous as to leave unclear his views on their relevance for Korea. The Bulletin’s editors were somewhat less restrained. They followed Oppenheimer’s article by reprinting a slightly shortened version of a piece by General Gavin entitled “Tactical Uses of the Atomic Bomb,” which originally appeared in the Combat Forces Journal. In their introduction the editors suggested that Gavin’s views were perhaps not shared by his superiors, but that “it is conceivable that the situation might present itself in a different light, when, in the course of military operations, a very large concentration of enemy troops might be forced to assemble in a limited area.”
The Korean War gave rise to fears of “another Korea” in Europe: a Soviet invasion across the inter-German border. Here, the proponents of tactical nuclear weapons found their most promising scenarios. Between the spring and fall of 1951, the California Institute of Technology, where Oppenheimer had worked before the war, hosted a large top-secret government study called Project Vista. The study focused on ground and air tactical warfare in European defense. Although Oppenheimer was not among the more than a hundred specialists who participated in the research, he was invited to draft one of its key chapters and to brief General Dwight Eisenhower, NATO’s supreme commander, on its findings. Vista’s recommendation to develop a range of atomic weapons suitable for use on a European battlefield proved highly threatening to the US Air Force, whose Strategic Air Command sought a monopoly on nuclear warfare. Air Force officials joined the H-bomb proponents, including Teller and Strauss, to help secure Oppenheimer’s downfall in the 1954 security clearance hearings.
Whatever impression Nolan’s movie conveys, it was not Oppenheimer’s moral qualms about nuclear weapons that incited such strong opposition against him. It was his challenge to the city-busting strategy of the Air Force and his advocacy of widening the range of uses for atomic bombs. In that respect he succeeded: During the Cold War, the United States deployed thousands of nuclear weapons for use in Europe, and the Soviet Union quickly followed suit.
The end of the Cold War led to vast reductions in the US and Soviet arsenals. But the Russian invasion of Ukraine has again raised the specter of nuclear war. Reported US plans to integrate new B61-12 nuclear weapons onto US- and NATO-operated tactical aircraft in Europe—to be used on the battlefield, just as Oppenheimer envisioned nuclear weapons could be used—will only make matters worse. The paradox of tactical nuclear weapons—clear already in the 1950s—remains the same today: Their use will destroy what they are intended to defend. And possibly more.
 Oppenheimer to Truman, 3 May 1946, Papers of Harry S. Truman, President’s Secretary’s File, box 201, folder, “Atomic Energy—Russia,” Harry S. Truman Library. Cited in Matthew Evangelista, Innovation and the Arms Race (Ithaca, NY: Cornell University Press, 1988).
 WSEG, Status Report, 1 November 1949, RG 218, Records of the United States Joint Chiefs of Staff, CCS 334, WSEG (2-4-48), sec. 2; James M. Gavin, War and Peace in the Space Age (New York: Harper, 1958), 114.
 Gavin, War and Peace in the Space Age, 116.
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