Introduction Globalizing Physics: One Hundred Years of the International Union of Pure and Applied Physics. An Introductory Essay

Physics played a major role throughout the 20th century in both wartime and peacetime. It underwent a major conceptual reconfiguration at the turn of the century with massive and long-lasting cultural and philosophical impacts. After World War II, physics came to be perceived, especially because of the atom bomb project, as the discipline whose development was decisive to national security, hence shaping the politics of the Cold War. Authoritative physicists became part of national Advisory Boards, thus playing crucial roles in the configuration of national and foreign policies, as well as acquiring enormous scientific prestige internationally.

Given the relevance of physics in contemporary history, it is perhaps surprising that the scholarly literature overlooks the history of the most authoritative international organization devoted to physics that globally unites professionals of this discipline: the International Union of Pure and Applied Physics (IUPAP). As of 2022, the year of IUPAP’s centenary, the only work exploring its past is a short booklet issued for the 70th anniversary of the Union and listing major events and figures. Former officers of this international organization have written short articles on its history too, but none extensive enough to shed light on its origins and evolution.¹ This volume therefore fills an important gap in our knowledge of the Union’s history. It does so through contributions addressing both general developments and specific cases that highlight key aspects of IUPAP’s role in both physics and international affairs. All the contributions display how the Union pursued its mission in a changing historical context, shaped by a variety of external social and political factors.

IUPAP’s current officials played a key role in the project leading to this volume as, while preparing for the centenary celebrations, they promoted the digitization of its entire institutional archive so that the scholars involved in the project could share and analyze these historical documents.² In COVID times, this proved invaluable since contributors to the collection worked in institutions located in four different continents and, due to the pandemic, could not travel to archives either. IUPAP also co-financed, together with the Donostia International Physics Center (DIPC), the hybrid workshop held in San Sebastian in October 2022 where, at the end of the pandemic, these scholars met to discuss the drafts of their original articles. IUPAP’s support was thus immensely important, though not alone in supporting the project. The combined efforts of the newly established Inter-Union (IUHPST/IUPAP) Commission on the History and Philosophy of Physics (IUCHPP), and the International Union of History and Philosophy of Science and Technology (IUHPST)/Division of History of Science and Technology (DHST) Commission on Science, Technology and Diplomacy (STAND) further contributed to the completion of this project.³

This volume charts the history of IUPAP as a crucial case study of the institutionalization of international science through the setting up of scientific unions and its umbrella organization, the International Council of Scientific Unions (ICSU). Originally conceived as the International Research Council (IRC), in 1931 it was re-named as ICSU and has since then been the main forum to coordinate international activities of various scientific unions.⁴ Volumes written on the history of ICSU and its unions have been a valuable reference, but our approach has been considerably different. Such historical studies are monographs that seek to provide an overall perspective of the activities of the unions. Often written by scientists and officers, they usually offer a first-hand perspective of the organizations in which they had been personally involved.⁵ Other monographs written by professional historians still offer synthetic narratives of the inner workings of scientific unions.⁶ And some projects assembling both scientists and historians have provided interesting collections devoted to a variety of aspects of some unions’ institutional history.⁷

This edited collection adds a historical analysis to these views that situates the history of IUPAP in the broader literature on science and international relations, also building on the bourgeoning literature on transnational historiography of science and technology.⁸ In this respect, the volume also draws on a recent edited volume focusing on the relationship between science and diplomacy in the context of the International Astronomical Union (IAU).⁹ All these new narratives shed light on the important role that scientific unions have played not just within the scientific world, but also in addressing, as a sort of “parallel” or track-II diplomatic forum, the relations between states and international political organizations globally.¹⁰

In 1963, a key figure in IUPAP’s history, the Canadian physicist and IUPAP Secretary General Larkin Kerwin, stated that “the Union’s purpose is to foster international physics meetings, more rapid dissemination of information and the establishment of international standards, units and nomenclature;” but crucially added that “[i]ts unofficial goal is to make a contribution to general international understanding.”¹¹ As our research moved on, we realized that this science diplomacy component was a major driving factor in the development of the Union.

Thus, our approach in writing the history of IUPAP has been different and more ambitious than previous historical accounts of international unions. In addition to in-depth analyses of case studies and themes, some contributors (including the two co-editors) carried out the task of writing articles that address the historical unfolding of the institution in more general and synthetic terms, thus placing specific themes and analyses into a long-term narrative. Overall, we collectively aimed at interpreting the history of IUPAP as a case study to investigate the complex dynamic relations between science and international politics in its historical unfolding and global repercussions. Contributors have thus focused on critical questions such as the roles IUPAP played in the scientific and political arenas (and the interaction thereof); or the Union’s dependency on broader historical transformations connected to globalization. The following synthetically recalls some of the general themes that have emerged in addressing these questions.

IUPAP was part of a network of scientific organizations that, strictly speaking, operated outside the sphere of governmental affairs but that, in fact, integrated in the activities and policies of governments and multilateral organizations. In examining these operations, IUPAP reveals itself as an organization practicing what we call today science diplomacy.

While many international scientific institutions have attracted the interest of historians of science, most accounts focus on project-oriented organizations, often operating in the European context. United Nations Educational, Scientific and Cultural Organization (UNESCO) has also received overwhelming attention as the main intergovernmental body devoted to the promotion of scientific and cultural exchanges (as well as education).¹² Over the last decade, interest in the history of international scientific institutions has grown, catering for a broader coverage, and offering readings that have also challenged the conventional understanding of the Cold War as a bipolar conflict through analyses of the global impacts of science and technology.¹³ The emergence of science diplomacy as a key aspect in international affairs in both scientific and political circles has further increased historians’ interest in the activities and functions of international organizations.¹⁴ The parallel historical reflection on the notions of scientific internationalism and universalism has shed light on the institutions that negotiated, defined, and operationalized these notions in the international arena.¹⁵ Finally, the increasing interest on transnational networks in connection with the growth of application of social network analysis as a methodological tool, has also led to reconsidering international scientific institutions as primary objects of investigation.¹⁶

One key issue is whether international scientific institutions depend on the official involvement of governments. The 1945 United Nations (UN) Charter sanctioned a distinction between intergovernmental and non-governmental organizations (IGOs and NGOs) also setting general principles for their operations.¹⁷ Works charting the history of scientific IGOs seem prevalent when compared to those looking into that of scientific NGOs, but it is important to emphasize that their evolution is marked by networking activities enmeshing one group of organizations into the other and establishing ties that complicate any effort to easily define the constellation of international scientific organizations departing from this distinction.¹⁸ So, like all other unions and ICSU itself, IUPAP is categorized as an NGO, even if over the post-war period it was lavishly funded through the intergovernmental UNESCO. Moreover, the legalistic characterization of IUPAP as an NGO works mainly from 1945, since the status of the Union as an international body was by and large undefined in previous decades.¹⁹

Historians and sociologists of science interested in international scientific institutions have put forward alternative taxonomies of such institutions partly in an effort to overcome the theoretical impasse that a strict distinction between scientific NGOs and IGOs outlines, and have looked into their modes of operation in scientific internationalism instead. Crawford et al., for instance, distinguish between spontaneous and bureaucratic institutions.²⁰ Spontaneous are “institutions motivated by the interests of individual scientists who draw on national resources to hold world congresses, committees, coordinate projects,” while the bureaucratic institutions are organizations whose “cooperative schemes are […] outgrowths of government programs and therefore strongly influenced by national interests.”²¹ The authors consider scientific unions and ICSU as aligned with the former model, while UNESCO exemplifies the latter. Aant Elzinga, similarly, differentiates between autoletic and heteroletic organizations, the former serving “science as an end in its own right” and the latter supporting “transnational scientific cooperation on extra-scientific grounds.”²²

Although IUPAP legally identifies as an NGO and should fit the definition of a spontaneous or autoletic mode of operation, various chapters in this volume show that this was hardly ever the case. In most part of the interwar period, all unions of the ICSU family were the embodiment of a political project extending World War I military alliances into post-war scientific cooperation. The institutionalized boycott of German physics discussed in the chapters by Fauque and Fox and Navarro, demonstrates that during the 1920s and 1930s IUPAP was fully implicated in the geopolitical dynamics of allied governments. Similarly, most chapters dealing with the history of IUPAP in the post-World War II period explicitly frame the Union as a venue for science diplomacy exercises, which had implications for the interactions between individual governments, multilateral organizations, and in some cases,—e.g., the German Democratic Republic (GDR), the People’s Republic of China (PRC), and the Republic of China (ROC) in Taiwan—even for the international recognition of these countries.

As mentioned previously, science diplomacy has recently emerged as a powerful buzzword at the intersection of studies on science, science policy, and international relations.²³ Historians have contributed to explore its past dimensions hence providing new analytical frameworks and key case studies.²⁴ This new literature (partly elaborated in connection with initiatives of the STAND Commission) has contributed to appraise the conventional understanding of science diplomacy as an inevitably beneficial tool in international relations. This idealized view, as Science and Technology Studies (STS) scholars Charlotte Rungius and Tim Flink contend, reiterates a simplistic understanding of science as inherently neutral and apolitical.²⁵ Many chapters in this volume capture historically contextualized science diplomacy exercises in which IUPAP was involved or featured as main actor, often explicitly using science diplomacy as an analytical framework.

Silva Neto and Kojevnikov show, for instance, that the Soviet entrance in IUPAP marked an appraisal of the notion of socialist internationalism and, contingently, of Soviet participation in international organizations. While membership to socialist multilateral organizations continued to be a key asset for the USSR, Soviet policymakers now embraced a parallel policy of acceptance of organizations uniting representation from both blocs. This recognition transformed international scientific cooperation in a device of Cold War détente, implicitly reiterating the stance of peaceful co-existence of communist and capitalist blocs. Within this co-existence, as Hof’s chapter shows, new dynamics of competition and cooperation emerged, as evidenced by the setting up (in parallel with the USSR joining IUPAP) of a commission on high-energy physics. Hof argues that it was the rhetoric of “purity”—implemented by labeling high-energy particle physics as a pure research branch in opposition to applied nuclear physics—that enabled this cooperation.

Science diplomacy features preeminently in the chapters discussing long-standing issues regarding membership in IUPAP, mainly because of the controversies surrounding acceptance of national committees from the GDR (discussed in the chapter by Olšáková), and those from the PRC and the ROC (analyzed in the chapter by Hu, Liu, and Yin). The participation of these committees evolved into tense diplomatic issues since it happened at the time when the GDR and the PRC had no official recognition in the West as independent countries. Both ICSU and IUPAP attempted to manage the ensuing controversy by staying away from explicitly political claims and deliberating that a union’s acceptation of a national committee had no implication for the international recognition of the respective states or governments. Yet, since this recognition was highly contested in the Cold War climate, it transformed IUPAP into a parallel diplomatic arena adjacent the UN forum where the debate on their status was articulated. These requests of admission into IUPAP arrived all within a few months in the period 1958–59 and implicated even more actors, such as for instance the members of the West German National Physics Committee unwilling to accept another German committee. US Department of State officials were deeply involved too (and anxious), given their support for ROC’s recognition and the parallel opposition to that of the PRC which they avowedly opposed (as argued by Hu, Liu, and Yin).

Even when these controversies ended, they had ramifications in another international conflict between IUPAP and the North Atlantic Treaty Organization (NATO) over the banning to travel of individual scientists from East Germany to NATO countries. As argued in Turchetti’s chapter, the tensions produced by the ban were formative of IUPAP as a science diplomacy organization in that the strong position taken by its President, the Indian physicist Homi Bhabha, marked the beginning of a more visible presence of the Union, globally, in the political arena through campaigning for the free circulation of scientists. In turn, this transformation defined one of the primary goals of IUPAP and ICSU in later years as a specific pledge in favor of East German scientists turned into a global one for any world scientist who could not travel to international conferences.

This science diplomacy framework also helps to capture many other instances when IUPAP’s activities had implications for state affairs, from Latin America to East Asia, such as in the case of the organization of the International Conference of Theoretical Physics in 1953 Japan (as discussed by Ito), and that of the Soviet-Italian physicist Gleb Wataghin (portrayed in Da Silva’s chapter). All these analyses challenge the simplistic division of international collaborative work into IGOs and NGOs, and uncover the existence of an extensive network comprising both. They also reveal IUPAP as a decisive cluster of this global network.

In turn, they lend further support to the view that over the last one hundred years IUPAP was more than just an organization devoted to assembling physicists internationally for the sake of advancing physics. Indeed, they display that IUPAP, as an international organization, built bridges (and at times tensions) between governments, regardless of its institutional status as an NGO. Globalization was a factor in this transformation. There is a bourgeoning literature in international relations studies explaining the deep impact of non-state actors—defined as actors whose actions are not necessarily officially endorsed by Governments—in international affairs.²⁶ Non-governmental institutions are among those non-state actors that transnational historians have recently considered as key in influencing world affairs especially with the weakening power of traditional state-to-state interactions and the opening of a new global sphere of decision-making mediated by multilateral organizations.²⁷ Science studies scholars have contributed to the effort to chart this transformation by arguing for the co-production of global scientific knowledge and global political order.²⁸

To sum up, we have studied IUPAP by breaking up conventional separations distinctive of international scientific organizations. Consequently, we contend that it is impossible to understand the Union as purely spontaneous or autoletic. Indeed, we show that the history of IUPAP displays a constant oscillation between autoletic and heteroletic modes of operation, depending on the political contexts that shaped these relations and the function of science in wider international issues debated at the time. As Lalli argues, IUPAP should rather be understood as a hybrid science diplomacy agent, constantly balancing between governmental and non-governmental interactions. In what follows, we show how this new approach assists in better understanding IUPAP’s scientific attainments over the one hundred years of its existence.

Historical theories of knowledge evolution see scientific institutions as regulative infrastructures that allow codifying, embodying, enabling, and transmitting knowledge across human society.²⁹ The dimension of internationality complicates this picture because the kind of social structure related to such institutions necessarily require to take into consideration the dimension of international politics. Crawford et al. have argued that the primary function of international scientific institutions has been to negotiate and define standards at the international level, at least in the period between the second half of the 19th century and the first decades of the 20th century. In their view, these standardization efforts acted at three levels: the pursuit of cognitive homogeneity within disciplines or emerging research areas, the establishment of shared communication standards within the largest scientific or disciplinary communities, and negotiations about technical standards often related to commercial needs in an increasingly global market.³⁰

Our investigations into IUPAP’s history further complicates this picture. Standardization, at the cognitive and communication levels, was indeed one of the Union’s primary goals since its establishment in 1922, as demonstrated especially by the setting up of its Working Commission on Symbols, Units, and Nomenclature (SUN) in 1931 (discussed in the chapters by Fauque and Fox, and Navarro). In particular, the mission of the commission was perfectly in line with the description of the pursuit of cognitive homogeneity in physics as described by Crawford et al. Before 1947, the other existing commission was the one on publications which, though rather irrelevant, confirms the centrality of standardization processes in IUPAP’s actions, in this case in the search for standards in the main scholarly communication venue in physics, namely, scientific journals. Standardization also remained a major focus of attention for IUPAP after World War II, with the SUN Commission becoming one of the most relevant within the Union (from 1966 in connection with other ventures, such as the establishment of the Committee on Data of the ICSU, CODATA).³¹ Doran’s chapter further exemplifies the importance of this aspect by looking at how light instruments enabled precision measurement and how IUPAP became a venue, albeit not the only one, where metrological negotiations took place.

That said, standardization was far from being the only area of intervention of IUPAP after it restarted its activities in 1947. As shown by Lalli, while the refoundation centered on re-establishing clear and well-defined relations between physics and politics in IUPAP actions, the result was the blossoming of topical commissions devoted to specific sub-fields of research (Figure I.1). In part, the creation of commissions might be interpreted as a standardization process of an international community defining the sub-disciplinary architecture of physics. However, what was being produced was a social disciplinary structure of physics with definitions of hierarchies, both social and cognitive. In addition, commissions had often the ambition to organize the field of research in a project-oriented fashion. Overall, the chapters in the volume demonstrate how standardization gradually lost its primary position in the framework of IUPAP activities since the early Cold War period. Lalli argues that the creation of topical commissions was the activity that most characterizes a radical shift in IUPAP’s role from an organization primarily aimed at providing standards into an organization that aspired to lay the conditions for scientific exchanges and actual cooperation.

Boundary work was being pursued in the process of forming commissions, in the negotiations within a commission, and in the relations between commissions, often leading to recognizing the necessity of cooperation among commissions for addressing specific topics.³² Intra- and inter-commission negotiations could actually be problematic, as shown by Fauque and Van Tiggelen in the case of the Joint Commission on Radioactivity, which IUPAP shared with the International Union of Pure and Applied Chemistry (IUPAC). Indeed, the boundary between disciplines (physics and chemistry), between epistemic traditions (in the evolving field of radioactivity), between institutional interests (the claims to preserve the pre-eminence of Curie’s laboratory), as well as the affinity or animosity between individual scientists (Frédéric Joliot-Curie), shaped the formation, evolution, and in this case, the demise of commissions and inter-union commissions.

IUPAP was also an instrument to globally navigate the relations between pure and applied physics. Martin shows how the emergence of a distinction between putative pure and applied realms depended on an ambition, especially in the US context, to motivate investments in basic research. This distinction did have an impact on IUPAP activities defining an imbalance in favor of non-applied research. Cold War imperatives, as shown in Hof’s chapter, heightened this imbalance further in the name of “purity” in relation to high-energy particle physics, whereas support to physics activities in developing countries, in line with UNESCO’s agenda, tipped the balance slightly in favor of applied (industrial) physics.

Support to developing countries, when combined to another key item in UNESCO’s agenda, i.e., education, also shows the widening scientific interests within IUPAP in the post-war period as a matter of diplomatic engagement with the UN agency, which can be seen in the proceedings of the Union’s Commission on Physics Education. As Simon’s chapter shows, however, there was a significant mismatch between preconceived views on what IUPAP wished to prioritize and the actual status of physics education in developing countries. Moreover, IUPAP’s efforts to promote industrial physics at the end of the century reflected the Union’s ambition to become a global actor.

But since IUPAP was part of an organizational structure for international science, with all unions integrated in an umbrella organization centered in ICSU (see Figure I.2), and this umbrella organization faced similar issues related to changing political context, it is legitimate to wonder to what extent IUPAP’s attainments, in the scientific and policy realms, were unique. Various chapters in the volume reveal this to be the case.

A premise is in order. The relations between ICSU and the unions changed considerably over the years. Until the creation of ICSU in 1931, unions were essentially IRC sections. After its establishment, unions had a greater degree of autonomy. The 1946 agreement between ICSU and UNESCO changed these relations again, for while decision-making within unions remained largely autonomous, UNESCO funding was made available for international conferences and joint commissions, hence shaping their initiatives and instigating competition between unions.

However, while sharing an interest in taking part in this race, IUPAP shaped an almost unique profile as a science diplomacy organization by embracing critical decisions regarding membership and the free circulation of scientists that other unions (or even ICSU at large) would not endorse so wholeheartedly. Why physicists were more ready than other kinds of scientists to take bold stances on matters of global relevance regarding international science is difficult to say. It is worth reminding, however, that since the end of World War II physicists have played politically relevant roles in various other arenas. Many had been involved in the campaign against nuclear proliferation and paid the price for this involvement through McCarthy’s witch-hunt.³³ Some institutionalized this campaigning through transnational political organizations like Pugwash.³⁴ Especially during the war in Vietnam, the physics community split over the contribution that physicists should have given to the conflict, some advocating advising US government while others considering these advisory roles as contributing to a genocide in Vietnam.³⁵

It should not be a surprise therefore that IUPAP officials were virtually at the forefront of a number of campaigns eventually endorsed by ICSU and the other unions. IUPAP was, for instance, the first union to offer national membership to an East German scientific organization. It is true that, as Olšáková shows, in so doing IUPAP was simply the first union to fully implement the principle of political non-discrimination that ICSU had already approved at its 1958 general assembly. Even so, its leaders displayed a considerable level of boldness, given that the matter of acceptance of an East German organization was highly contentious at an international level due to the non-recognition of the East German state in the “free world.” As discussed in Cozzoli’s chapter, the then President Edoardo Amaldi in particular must have been aware that IUPAP’s move would produce a domino effect, with East German committees separately requesting acceptance in ICSU and other unions, and making it difficult for their officials to refuse it in light of the precedent set by IUPAP.

Likewise, the IUPAP Executive Committee agreed to accept the Physical Society of Taiwan without waiting the formal indication by ICSU, in spite of proposals to wait for ICSU’s decisions on these matters. As shown by Hu, Liu and Yin, the controversy regarding the PRC and ROC membership extended to other unions, but in the combined acceptance of Taiwan and GDR as national members in 1959, IUPAP pioneered an argument based on a symmetry in relation to the opposite pressures of Cold War blocs.

The highly divisive issue of the free circulation of scientists displays once again a pioneering role for IUPAP. As shown in Turchetti’s chapter, IUPAP took the lead in forwarding an official protest to NATO for the ban to East German scientists travelling to Western countries. Bhabha’s letter to the NATO Assistant Secretary General for Scientific Affairs informed further correspondence by the ICSU Secretary and Executive Board who extended the Indian physicist’s pledge, paving the way to the establishment, in 1963, of an ICSU Standing Committee on the Free Circulation of Scientists.

IUPAP’s development as a scientific organization also differed from that of other unions. As discussed in the chapters by Fauque and Fox, and Navarro, IUPAP often operated according to a discipline-specific agenda. It was mostly inactive in the period between the two World Wars, and the only two scientific commissions established were general in scope, primarily dealing with standardization. This was in stark contrast to the IAU, which by the early 1920s had already created thirty-two commissions dedicated to specific research topics. It remained in the middle ground between unions that put forward scientific agendas despite the limitation of the international participation due to the exclusion of Central Powers’ scientists, like the IAU, and those unions that were completely dismantled because of the political issue of exclusion of Germans, like the International Mathematical Union (IMU). In a way, the interwar period saw IUPAP failing in many respects, especially in the involvement of Germans, but it was precisely the decision to continue maintaining the existence of the organization despite these failures that allowed IUPAP to resurge from its ashes after World War II and gain a central place in the international re-organization of physics.

Hence IUPAP was not simply and not only a manifestation of broader processes of international scientific coordination applied to the physics realm. It was a venue for autonomous decision-making processes where physicists were the primary actors in relations to governments, other institutions, and networks of similar organizations under the ICSU umbrella.

The issue of autonomous decision-making calls into question another key issue that this volume posits; namely, to what extent individuals informed institutional decisions at IUPAP. Drawing on works that have revealed the multiple roles that some scientists could play in the international arena (as policymakers and at times even intelligence agents), the chapters in the volume display the significance of individual interventions in era-defining issues for IUPAP’s history.³⁶

The role of IUPAP Presidents in designing and implementing specific agendas is particularly evident in these analyses. For instance, Navarro shows how the energetic US physicist Robert Millikan saw IUPAP as an important platform for extending a US hegemony over the physical sciences during the 1930s, and his promotion of an enlargement of IUPAP to former enemy countries further confirms this ambition. Millikan’s attempts were largely unsuccessful, but they show how individual agendas modelled actions and membership in the Union.

Edoardo Amaldi had an equally central role in shaping Italian physics in the decades after World War II and in institution-building at the European level. Amaldi’s personal political stances and his central position in Italian policy-making in physics made him the ideal figure to lead IUPAP into a fundamental transition of its history, when the Union transformed into an institution based on the balance between Cold War blocs with the Soviet membership of 1957. As discussed by Cozzoli, Amaldi’s views in the negotiation opened the entrance of both Taiwan and the GDR as a manifestation of symmetry between Western and Soviet blocs. In addition, he proposed rules and norms that govern the functioning of IUPAP to this day.

In these negotiations, Amaldi was also responsible for promoting the election of Indian nuclear physicist Homi Bhabha as the next President, opening the presidency to representatives of developing and non-aligned countries. Bhabha then played a central role in his political protest of the NATO ban against East German physicists, which had momentous consequences for IUPAP as an international organization (as shown by Turchetti). The Soviet physicist Dmitry Ivanovich Blokhintsev, who was the IUPAP President in the period 1966–69, helped to implement a change of the notion of scientific internationalism that would enable Eastern bloc countries to join the Union more readily, as shown by Silva Neto and Kojevnikov. While only the activities of a few Presidents are discussed in detail in the volume, they reveal the continuous interplay between broader historical forces and the responses of individuals in positions of responsibility in the organization in particularly crucial historical transitions.

IUPAP meant a lot for individual physicists outside the organization’s leadership too. IUPAP is thus revealed in Da Silva’s chapter to have played a key role in the Russian-Italian physicist Gleb Wataghin’s attempt to establish cultural and scientific contacts with his former homeland Russia, exactly in the period when the Soviet Union joined international cooperation. Alignment of individual and institutional agendas is also central in the organization of the International Conference of Theoretical Physics in Japan that Ito discusses in his chapter. “The almost invisible ‘Japanese guy[s],’” Ito tells us, spent a considerable amount of their time in organizing the meeting to restore contacts with the international physical community after World War II, aware of the political implications of this opening. These efforts had scientific consequences as well, for the Japanese physicists themselves eventually got international scientific recognition, also through IUPAP.

IUPAP was not a simple manifestation of broader processes or implementation of decisions made elsewhere. IUPAP was a venue and an engine for negotiations at different levels in which individual agendas, institutional processes, and governmental imperatives interacted within the broader global political and scientific contexts to define the policies of the organization. Like other unions, and in relation to ICSU and the other unions, IUPAP then represents a privileged window to investigate two challenging and interconnected problems in the history of science.

The first problem concerns the dichotomy of universalism and contextualism in the natural sciences: while, on the one hand, natural sciences aspire to universality by virtue of their rigorous formal and experimental methods, on the other hand, like any human activity, they depend on situated historical and political contexts. The second involves the historical transformations of the ideal and practices of scientific internationalism and their impacts on science diplomacy during the twentieth century, namely, how the contextually dependent contrast between internationalist views and national constraints shaped scientific activities and, consequently, the function of scientific cooperation in international political relations.

Beyond the relevance of physics, the reasons for making IUPAP such a privileged point of observation of the previously mentioned issues is the fact that IUPAP is, and was, legally an NGO. This implies that its decision-making processes had necessarily to be discussed by individuals whose status was of non-state actors, whatever their covert or open connection with governmental agendas of their nations might have been. In addition, IUPAP is a generalist organization that is not dedicated to specific projects but to a discipline tout court, in this way allowing to study how the discipline has been built at the global level and how politics and science interacted in the socio-institutional process of discipline making.

IUPAP officers had to take their multiple roles in national and international science (and science policymaking) into account in all discussions related to scientific matters as well as to their relation to the broader political, economic, social, and cultural contexts. Clearly, the global promotion and advancement of physics was their main preoccupation, but it could not be the only one. They had to interpret physics tout court, and its evolving branches, as part of a complex global dimension, and a crucial one. By looking at IUPAP as a hybrid science diplomacy agent, and by discussing the interactions between scientists, other organizations, and governments in shaping its activities, the chapters in this volume have reconstructed key transitions in these negotiations, showing the non-trivial connections between global political and scientific orders.

It was not our intent to write a complete history of IUPAP since its inception to this day. Many relevant actors, events, and processes could not be discussed in detail. But we hope that the chapters dealing with case studies and the analytic views offered in this introduction and various chapters provide a framework both for interpreting the broad scopes of these scientific international organizations in their historical unfolding and for capturing the specific role IUPAP played in some key moments.