This is where the work of these two scholars connects in quite a direct way—in the creation of a system of rules for the management of the challenges of an age of nuclear weapons. This is not evident in Bull’s Anarchical Society—which does not cite the then Harvard University Professor, but which cites Coral Bell, and the sometimes overlooked but brilliant work of Morton Kaplan, and misspells Samuel Huntington’s surname. However, Bull’s earlier and magisterial Control of the Arms Race contains the politically incorrect argument that ‘the maintenance of a stable Soviet–Western balance may require high levels and advanced kinds of arguments, and may even be served by the further prosecution of the arms race in certain fields’.^[44] His footnote to that point is as follows: ‘The most persuasive exponent of these arguments has been Professor Thomas C. Schelling of Harvard University, to whose work on the theory of arms control, and especially on the problems of surprise attack, I an especially indebted.’^[45] It is important to note here that Bull not only cited relevant parts of Schelling’s Strategy of Conflict, but also two of Schelling’s journal articles from 1960 which indicate he was an avid reader of the American strategist.

Bull had visited the east coast of the United States in September 1957 and met Schelling.^[46] At that time the American thinker’s work on strategic bargaining and the limitation of armed conflict was gaining influence through the publication of essays which were to find their way into The Strategy of Conflict. It was also the period in which Bull was rejecting the much more absolutist logic of complete disarmament which he had encountered as a scholar assisting the former British politician Philip Noel-Baker.^[47] Bull’s assault in 1959 on Noel-Baker’s book, which had been published the previous year under the title The Arms Race, carries little direct sign of an awareness of Schelling’s work,^[48] but this influence was to become more apparent in Bull’s work within the next two years.

Bull’s Control of the Arms Race, officially the product of an Institute for Strategic Studies working group, but really the work of the author, found an admirer in Schelling who reviewed it in pre-publication form for the Institute’s new journal Survival. Schelling found it to be a ‘cool and competent envelopment of recent strategic thinking in a political treatise on international violence’.^[49] He applauded the ‘genius’ of Bull’s book in putting ‘the problem of war in political, historical, and moral perspective’^[50]—something the reviewer himself could not have been accused of doing. But it is evident that Schelling considered himself the more original thinker. He argues that ‘Bull’s careful analysis turns up no new ideas’, and might even have been thinking of his own Strategy of Conflict in arguing that, had Bull published a year earlier, it ‘would have been unique in its application of military reasoning to arms control’.^[51]

This is not an opinion shared by all. Robert O’Neill and David Schwartz, who two decades ago edited a retrospective volume containing Bull’s main works on arms control, call him ‘one of its most original and penetrating contributors’.^[52] Even so, a contrast can be made from 1961 between Hedley Bull, a young scholar not yet 30 whose broader ideas on international relations were still evolving, and Thomas Schelling, ten years his senior, who had by that time erected an enduring and mature framework of strategic analysis. In any case, Bull got his own back in a 1967 review of Schelling’s Arms and Influence. On the eve of his arrival as The Australian National University’s second Professor of International Relations, Bull wrote:

That last judgement may have been aimed at Schelling’s citation of Xenophon’s account of the Persian Expedition:^[54] far from being a long-term influence on his earlier theory, Schelling told me he in an interview that he had simply found the translation in an airport bookstand.

Schelling would himself publish an influential volume in 1961 on the same subject. This was Strategy and Arms Control ^[55] which Schelling co-authored with Morton Halperin. Along with Bull’s book and a collection edited by Donald G. Brennan,^[56] also published in 1961, these formed the trio of arms control classics for the nuclear age. Schelling and Halperin saw their work as being less concerned with the broader political context of arms control. They advertised their work as concentrating on the ‘military environment’ rather than the ‘more purely political and psychological consequences’^[57] of arms control. Indeed in an interview I conducted in 1996, Schelling told me that they had made a deliberate decision to exclude political considerations so as to emphasise the military element. To some extent this may have been a matter of brand differentiation; after all, they had access to an early draft of Bull’s book while writing their own text. But it also reflected Schelling’s theoretical predisposition as a microeconomist to use parsimonious models of strategic behaviour which assume away broader contextual factors.

Stanley Hoffman explains the distinction by stating that Bull’s

One of Schelling’s most vivid phrases is ‘the diplomacy of violence’,^[59] by which he means the informal and tacit but powerful messages which the use of armed force can deliver. Bull spent a good deal of his time appreciating the broader political and diplomatic context in which those messages might be transmitted.

This early 1960s connection between Bull and Schelling suggests a mutual respect between the two authors, and also a degree of competition in their approach. But what can it tell us about the title of this paper—their common interest in common interest? One sign of a connection in this regard comes in Bull’s discussion mid-way through The Control of the Arms Race of explicit arms control agreements between the powers. Cautioning against the belief in disarmament agreements as a solution to the competition for military advantage, he writes that

There are no footnotes to this section, but the italicised phrase ‘the striking of a bargain’ and the reference to other kinds of bargaining which advance both sides interests without harming either one of them is, in my opinion, close to pure Schelling.

For Schelling, strategy was all about bargaining situations. The ability to strike bargains was the secret to stable strategic relations. In The Strategy of Conflict, he writes:

This encapsulates the two points evident in Bull’s comment about arms control agreements: that they involve the striking of a bargain, and that they represent a common interest between parties who might otherwise harm one another’s interests if they are not able to agree.

Rather than Bull’s emphasis on explicit and formal arms control agreements, Schelling’s argument deals more with implicit or tacit bargains—where the parties somehow coordinate informally their behaviour around focal points which stand out from the background like the 38th parallel in Korea. Bull certainly has an interest in the informal arrangements which can produce order in the absence of formal government. In a conversation I was able to have in 2007 when she was visiting Australia, Mary Bull noted her late husband’s interest in tacit agreements and in Schelling’s work in this area. But Hedley Bull was, at least by 1967, not so sure about tacit agreements. He writes

This is not to imply that Bull regarded Schelling’s general contribution as wanting. In one of his most prominent essays published a year earlier, Bull argued that Schelling

My analysis of this Bull–Schelling connection may seem a little strained. After all, a good deal of the inspiration for Schelling’s argument about the striking of bargains by parties due to their common interest in avoiding mutual harm is associated from his non-zero-sum reformulation of game theory. Such formal and potentially pseudo-scientific treatments of international behaviour held little water for one of the founders of the English school of international relations who railed against false quantification. The immediately previous quotation praising Schelling comes from his essay ‘International Relations: The Case for a Classical Approach’, in which Bull made some fairly swingeing attacks on those who would view international politics as a science reducible to experimentally testable hypotheses.^[64]

But Schelling was a very unorthodox game theorist, interested not in the artificial production of numerical answers to qualitative problems, but in the powerful ideas which game theory helped isolate—including the interdependence of adversaries’ behaviour and interests. And in a 1972 essay, which ended up in Australian Outlook—the precursor to today’s Australian Journal of International Affairs—and which began as a paper read to an Australian National University Department of International Relations seminar, Bull points out that some of the formal theorists were more than worth paying attention to. Recalling the piece he had written some six years earlier, Bull writes:

And then he goes straight on:

In concluding this assessment, Bull nails the informality of Schelling’s formal theorising by saying: ‘My argument was that “scientific” theorists who had made significant contributions did so by failing to adhere to their own methodological principles and reverting to the “classical” style of argument.’^[65] Indeed in an earlier essay he had observed very shrewdly that ‘a number of strategists, like Thomas Schelling who have mastered this technique, but in their work exercises in game theory serve only to illustrate points that are independently arrived at’.^[66]

Bull’s comments could not have been more apt in terms of Schelling’s own scholarship. What Bull saw as admirable as a classical theorist was objectionable to the gatekeepers of the formal game theory. When Schelling’s Strategy of Conflict was reviewed by leading game theorist Martin Shubik, the following criticism resulted:

Schelling’s work was also criticised for similar formal inadequacies by Oskar Morgenstern^[68] (one of game theory’s giants), who wrote a few years later that ‘the theory of games is a mathematical discipline designed to treat rigorously the question of optimal behavior of participants in games of strategy and to determine the resulting equilibria’.^[69] Rather interestingly, Bull observed in 1968 that, ‘as far as I know, the only person who has claimed that game theory presents a method of solving strategic problems is Oskar Morgenstern of Princeton University’.^[70] It is quite clear that Bull regarded himself on Schelling’s side of the game theory debate. Not only did he reject the more quantitative approach, he also evidently had little time for the claims that Schelling’s adaptation of game theory to strategic thinking was dangerous, calling Anatol Rapoport’s work ‘wrong-headed but subtle and powerful’.^[71]