So much has been written about Tom Schelling’s enormous intellectual contributions. I would like to supplement these articles with a more personal account.

I first “met” Tom in print. As a junior at Oberlin College, I ran across The Strategy of Conflict. Without seeing all of its implications and nuances, I found it eye-opening. This is what politics, especially international politics, was all about: strategic interaction, which meant that each side was trying to anticipate how the other side would respond to its moves, knowing that the other side was doing likewise. One didn’t need formal game theory to grasp this or to follow out many of its leads. Among the most famous concepts he developed were the strategy of commitment and the reciprocal fear of surprise attack. Fifty years later, it is easy to forget how radical these ideas were at the time. The pre-Schelling literature on bargaining had noticed that actors sometimes staked out positions in public that made retreat much more difficult, but these incidents seemed aberrations, errors, or the product of emotions.

The academic community and members of the educated public simply did not understand what was going on. We had all missed one key idea. An actor that staked its reputation on standing firm and increased the costs it would pay upon backing down also increased the chance that its adversary, understanding this and seeing that the actor was now less likely to retreat, would have to make the concessions that were necessary to avoid a mutually destructive conflict. Those who opposed “hard line” policies toward the Soviet Union found this argument bizarre or dangerous, if not both, because it would reduce U.S. flexibility and paint the Soviet Union into a corner. But they found more appealing Tom’s notion of the reciprocal fear of surprise attack. Building on earlier work done at RAND on the “prisoner’s dilemma” and on Albert Wohlstetter’s arguments about the dangerous vulnerability of American air bases, Tom realized that wedding both produced further policy-relevant insights. American vulnerability was indeed dangerous, but Soviet vulnerability, far from being an unalloyed benefit to the United States, could lead to a war that neither side desired as each side, fearing the other might attack, rushed to strike first.

This was an era in which not only scholars and policymakers, but almost everyone, was worried about the twin risks of nuclear war and Soviet expansionism. It was far from clear how Soviet aggression could be combatted without greatly increasing the risk of nuclear war. The atmosphere combined intellectual confusion, political contention, and fear. In this context, Tom’s ideas offered both clarity and reassurance. Although he was not the only one developing arguments like this, the brilliance of the exposition gave him a wide audience. While his views carried weight with students and officials alike and made him a leading member of the foreign policy “establishment,” he retained a sense of how absurd nuclear strategy was. Critics may have thought that he was a figure like Dr. Strangelove, but they probably did not realize that he was an advisor to Kubrick when he made the film.

Critics from both the left and the right also blamed him for American policy in Vietnam. Conservatives believed that his writings on the controlled use of force predisposed the Johnson administration to titrate the bombing of North Vietnam in a slow escalation rather than applying decisive force. It is true that one of the architects of the bombing policy, Assistant Secretary of Defense John McNaughton, was a protégé of Tom’s, but the dominant reason for keeping the bombing limited was to limit adverse international reaction and to reduce the danger of Chinese intervention. By contrast, liberals believed that the administration’s acceptance of Tom’s theories had made it confident that it could prevail. However, thanks to declassified records, we now know Johnson lacked confidence and employed cruder thinking. What faith he had in an eventual American victory came from the knowledge that the United States was stronger than North Vietnam. Nixon did believe that he could force a settlement as a result of his “madman theory,” in which he would show the North and the Soviet Union that he might pursue a crazy escalation. While this resembled Tom’s tactic of “rationality of irrationality,” it probably owed more to Nixon’s view of the world than to Tom’s writings.

In Strategy of Conflict, as in his later work, one can see the foundation in and contribution to game theory. Indeed, the citation for his Nobel Prize was phrased in these terms. But as Tom often explained, although he devoured Luce and Raiffa’s Games and Decisions, his attitude toward game theory was ambivalent. Soon after we met, he complained that Hedley Bull was wrong when he claimed that his insights did not require game theory: “How could Hedley know how I arrived at my ideas?” Yet he once complimented me for a study I did of the evolution of American nuclear strategy by saying that I wisely did not discuss game theory!

In fact, Tom was a game theorist, but an unconventional one. Although his conclusions were often counterintuitive, he did not rely much on mathematics, instead drawing much more heavily on psychology, historical examples, and observations of human behavior in settings ranging from everyday life to wargames. It was theoretical, but deeply empirical, not only in the sense of being grounded in how people actually behaved, but also in the deep sense of knowing that it was the actors rather than the theorist who supplied the knowledge, values, and the definitions of the situation that created and ran the game.

My next exposure to Tom was at an arms control symposium at Swarthmore. It was a revelation to hear him speak in crystalline paragraphs with nary a false move. He argued for the fundamental point that the goal of the United States should be arms control, not disarmament. We should seek safety and stability, not lowered numbers for their own sake. Needless to say, I was not the only one who was impressed. American policy shifted from disarmament to arms control in subsequent years in response to the ideas of Tom and his colleagues. These were transmitted not only through publications, but by close contacts with policymakers. (Much of the first draft of Arms and Influence was produced as a top secret government report.) The lure of lowered numbers never entirely lost its sway, however, much to Tom’s displeasure.

In the 1960s, strategic thinking and game theory were subject to fierce attacks for justifying if not causing dangerous American polices. This debate was important to me in developing my ideas about the security dilemma and the clash between the deterrence and spiral models, the former arguing that an assertive foreign policy backed by a robust military would keep the peace, while the latter said that such a stance was in fact more likely to set off a spiral of hostility if not lead to war. More significantly, many of the critics failed to come to grips with Tom’s arguments on their own terms or to see that many of them actually led to policy recommendations they shared. The most obvious example is the rejection of the quest for nuclear superiority and warfighting options. Relatedly, they did not see that Tom’s approach called for understanding and empathizing with adversaries.

Perhaps it was his cool approach that created some of the confusion — I know it made problems for me personally. Tom’s analyses, widely shared in the strategic and arms control community, reinforced the point made by Bernard Brodie at the start of the nuclear era: What was revolutionary about nuclear weapons was not their enormous destructive capacity, but the fact that once retaliatory forces were secure, no one could win a nuclear war. In other words, the common talk of “overkill” overlooked that what was crucial was “mutual kill.” The problem, at least for me, was how he chose to put this. When he came to Berkeley in the mid-1960s, where he had earned his Ph. D. and where I was a graduate student, I urged all my friends to hear his lecture, both because I knew it would be incredibly lucid and because I was confident it would show that people like myself who were interested in nuclear strategy were normal human beings. Thanks to growing doubts about the Cold War and even more so to opposition to the American intervention in Vietnam, the focus of Berkeley protest movements (which was one reason I went there) had shifted from civil rights and civil liberties to international politics. Nuclear weapons, of course, were particularly unpopular. During his remarks, in arguing that the notion of overkill was misleading, he drew from the draft of Arms and Influence and explained that if the United States had chosen, it could have killed everyone in Japan after the end of the war. This showed that the possibility of overkill was not new and so established his point. Unfortunately for me, however, he did not stop there but went on to say that we could have done the killing “with icepicks,” and all the progress I had made in convincing my friends that nuclear strategists were not monsters vanished in an instant.

Schelling’s ability to convince more important audiences of the validity of his arguments was greater, although many analysts joined him in these endeavors. Once he elucidated the virtues of the tactic of commitment, scholars saw it in many encounters — in the stationing of American troops in Berlin, in the formation of NATO itself, and in speeches by Johnson and Nixon declaiming that if the United States did not “stay the course” in Vietnam, neither allies nor adversaries would trust their promises and threats in the future. This was not merely an American trope. At the Vienna summit meeting, Nikita Khrushchev told Kennedy that he could not retreat from his pledge to sign a peace treaty with East Germany and drive the West from Berlin. (Kennedy took this very seriously and in fact was willing to make serious concessions to reach an agreement. Fortunately, he did not have to, as Khrushchev backed off after the Cuban missile crisis.) But three notes of caution are necessary. First, the tactic of commitment is dangerous. It increases the cost to the actor if it is forced to back down (this is not a side-effect, but is the motor of the maneuver) and, as in the game of “chicken,” if both sides remain committed, a deadly collision will result. Second, although examples of commitment are easily found, even now we lack systematic research as to its prevalence. Decision-makers naturally want to keep their options open rather than foreclose them, as the tactic calls for. Third, to the extent that we find commitment to be common in the years after Schelling wrote, it may have been because he convinced decision-makers by his lucid logic rather than his having discovered a pre-existing pattern. Academics often like to exaggerate their influence, but Tom’s logic was so compelling that it may actually have been a case of a theory validating itself through persuasion.

Another of Tom’s arguments may also have influenced policy. Starting in the 1950s, when American leaders realized that it was only a matter of time before Soviets could hold the American homeland hostage, they worried alongside scholars about maintaining “extended deterrence” — the ability of the United States to deter attacks on its allies by threatening to use strategic nuclear weapons to defeat a Soviet attack. Most scholars, commentators, and traditional game theorists saw little way out: The United States could hardly make credible threats to commit suicide. Tom’s ingenious response was “competition in risk-taking” and “the threat that leaves something to chance.” The movement from peace to war was not like flipping an on/off switch, because either side could take actions that raised the danger that things would get out of hand and that all-out war would result even if no one wanted it. Fighting a conventional war, even if the United States was losing, would run a significant risk of inadvertent escalation, and this could deter the Soviets from starting such a war even if they believed they could win it as long as it stayed under control. Tom refined this idea in 1961, when the Kennedy administration was facing increased Soviet pressure on Berlin. The prevailing view was pessimistic and belligerent in the winter and spring, as it operated within the earlier intellectual framework that viewed “chicken” in all-or-none terms. Yet after McGeorge Bundy, Kennedy’s national security advisor and a former colleague of Schelling’s, put a paper of his into the president’s weekend reading packet, American policy soon changed (although whether this was cause-and-effect is impossible to know). But if nothing else, Schelling’s ideas years later became a centerpiece of my two books on nuclear strategy, The Illogic of American Nuclear Strategy and The Meaning of the Nuclear Revolution. These books made my reputation in the nuclear strategy field, but largely were a repackaging, reimagining, and elaboration of Schelling’s ideas (with additional major debts to the scholarship of Glenn Snyder, my teacher at Berkeley, and Bernard Brodie, my colleague at UCLA).

My debt to Tom did not end there. Although I had never met him, in early 1966, I sent him my dissertation proposal on signaling and perception and said that I was coming east for a week. He replied that although he was spending a year in the United Kingdom, he was making a trip back to Harvard and could see me on a Saturday when he would be in his office catching up on his mail. It took years for me to fully appreciate how generous this was, but it made all the difference to my career. He saw in the proposal more than was there and offered not only to put me on a panel in the fall American Political Science Association meetings, but to support me for two years of research at Harvard. (Tom’s taste was eclectic. He also supported Gene Sharp, who was writing on non-violence protest.) This allowed me to write my dissertation, which became The Logic of Images in International Relations, which combined Tom’s ideas with those of Erving Goffman’s Presentation of Self in Everyday Life, in turn influencing another student of Tom’s, Michael Spence, who was also working on signaling. Tom later said that he thought my book was entirely original and could not see where the thoughts came from, but the answer was largely in his own work.

In my two years of research, Tom’s support was more than financial. Harvard was not the friendliest of climates for young scholars, especially for those without a Harvard Ph.D. He was always generous with his time and opinions, as well as in inviting me and my wife to dinner parties. Without these two years of supported research and encouragement, coming at a time when my Ph.D. committee could not understand what I was doing, I doubt whether I could have had much later success.

Even after I left Harvard, Tom’s encouragement and ideas remained central. He moved away from nuclear strategy, as I did after the Cold War. He continued to elaborate complex ideas of strategic interaction, however, culminating in the essays collected in Micromotives and Macrobehavior. These were filled with ideas about tipping points, cooperation, and, as the title indicates, the radical disjunctions between what any individual intends and what the interaction produces. Feedbacks, nonlinearities, step-level changes, and multiple complexities can follow as individual actions ramify throughout an inter-connected system. This was a way of understanding the emerging field of complexity without resorting to mystification or mind-numbing abstractions, and it was foundational to my System Effects.

Tom retained his interest in nuclear issues, even if they no longer preoccupied him. As the topic of his 2005 Nobel Prize lecture, he chose the “stunning achievement” that nuclear weapons had not been used after Nagasaki despite the common predictions to the contrary. Interestingly enough, he attributed this not only to the ideas of deterrence that he had helped develop, but also to the “nearly universal revulsion against nuclear weapons,” a factor beyond the ken of standard game theory but easily brought into his thinking. He also continued to think in terms of dynamics and anticipations, which led him to reject proposals from the “global zero” anti-nuclear weapons movement. This was not because the notion was idealistic, but because, as he pointed out over 50 years ago, such a world would be highly unstable because nuclear states would still have not only the knowledge of how build these weapons, but the knowledge that their peers did as well, leading to strong incentive to build and strike first. Indeed, one of the few times I saw Tom come close to losing his temper was when we talked about Henry Kissinger’s endorsement of nuclear abolition, because Henry should have known better.

I simply cannot imagine where social science would now be without Tom’s ideas. I know that my own intellectual world would be infinitely poorer without his thoughts. My professional career could not have flourished without them, and my personal life was greatly enriched by his friendship. He will be sorely missed.

Robert Jervis is the Adlai E. Stevenson Professor of International Politics and has been a member of the Columbia University political science department since 1980.