As the ambitious projects to govern globalization in the wake of the Cold War have faltered, historians have developed a more nuanced understanding of the history of internationalism, starting with the League of Nations. New research has complicated the established narrative of interwar crisis and failure—which focused on collective security—by demonstrating that the League of Nations had an enduring institutional impact in many other areas, especially in imperial politics and economic cooperation. In Plowshares into Swords, David Ekbladh makes a valuable contribution to this debate by providing the first systematic analysis of US participation in the technical work of the League of Nations.

Ekbladh draws together several lines of research on the history of the League of Nations that have emerged over the last twenty years. Early studies revealed the networks of knowledge and expertise that developed around the League and made it possible to conceptualize multilateral economic intervention on a world scale (Anthony Endres and Grant Fleming, International Organizations and the Analysis of Economic Policy, 1919–1950 [2002]; Yann Decorzant, La Société des Nations et la naissance d’une conception de la régulation économique internationale [2011]). Subsequent work showed that economic policy gradually expanded to assume a dominant position in the broader architecture of international governance, as the League’s efforts to promote political cooperation broke down in the 1930s (Patricia Clavin, Securing the World Economy [2013]). Recently, there has been a move to reassess the League’s core security mission and its relationship to the world wars, in light of the new scholarship on economic cooperation (Nicholas Mulder, The Economic Weapon [2022]). Scholars have also begun to look deeper into practical mechanics of interwar internationalism, uncovering the manifold organizational channels that fed into the postwar settlement after 1945 (Simon Jackson and Alanna O’Malley, The Institution of International Order [2018]; Karen Gram-Skjoldager, Haakon Andreas Ikonomou, and Torsten Kahlert, Organizing the 20th Century World [2020]; Jamie Martin, The Meddlers [2022]).

Plowshares into Swords builds on this scholarship to reexamine the League of Nations from the outside-in. The narrative is driven by associations and individuals who engaged with policy projects in Geneva, at varying degrees of remove. Ekbladh highlights how non-members, chiefly the United States, supported the central pivot in the history of the League from politics to economics. In the 1930s, US-based internationalists pushed to strip the Versailles regime of collective security out of the League’s work and to prioritize material welfare, helping to forge “plowshares.” They then fashioned new “swords” during the Second World War by drawing on the resources of the League’s Economic and Financial Section to prosecute industrial warfare and to define the Allies’ war aims (though the book mostly concentrates on the latter point).

The body of Plowshares into Swords is divided into four essays that build a chronological narrative. The first chapter traces the development of new institutions to promote a data-driven understanding of the world economy, both in the United States and in the League. The second chapter recounts how this system of economic cooperation was put on public display at the New York World’s Fair in 1939, just as US internationalism took on a harder edge with the outbreak of the Second World War. The third chapter follows the League’s economic team through the war, as they transferred their base across the Atlantic to the Princeton Institute for Advanced Study and began to engage more actively in US policymaking. The final chapter shows how the tools of interwar internationalism were redeployed in postwar planning, focusing on the issue of economic development.

Throughout the book, Ekbladh uses the concept of “international society” to capture collaborative relationships that were in dialogue with the League but often did not pass through it directly. This approach usefully highlights how people from around the world intervened to mediate the relationship between the United States and the League of Nations. However, the institutional architecture of collaboration and the underlying power relations sometimes become obscure. Ekbladh’s international society is composed of academics, philanthropic foundations, policy-advocacy nongovernmental organizations, as well as national and international civil servants. Readers of the Business History Review will note the absence of private businesspeople, who are mainly discussed as funders for other endeavors rather than as international agents in their own right. Ekbladh’s analysis would have been strengthened by including the private regimes of international economic order that were crafted by businesspeople and lawyers because they formed an important part of the League’s transatlantic bridge. For example, the first US representative in the League’s trade body was both a trained lawyer specializing in contract arbitration and a leader in the International Chamber of Commerce.

Overall, the book makes a strong case that the rise of the United States as a global power was a multilateral process that was not driven by US actors alone. US-based networks made a crucial contribution to the economic work of the League of Nations, and this long experience with multilateral outreach shaped the United States’ approach to international order during the mid-century transition. Plowshares into Swords will be of interest to historians working on US foreign relations, internationalism, economic development, and policy expertise. Indeed, the book positions the League of Nations as a central analytical node connecting all these fields.