Joseph Stalin once scoffed at the papacy's diplomatic power in the modern world, rhetorically asking how many troop divisions the pope had. Ironically, the soft-power moral suasion of the Polish pope, John Paul II, helped to topple Communism in Eastern Europe. Nevertheless, the Stalinist attitude lingers when discussing modern papal diplomacy, with the assumption that papal power is a decayed artefact of early modern history. The nineteenth-century process of Italian unification, seeing the pope humbled as a self-styled ‘prisoner of the Vatican’ surrounded by an aggressively secular Italian state, would seem to symbolise the papacy's enfeeblement against modern forces.

Giuliana Chamedes's excellent new book is a welcome corrective to standard narratives about the papacy's supposed irrelevance in modern international history. Chamedes convincingly argues that in reaction to the Russian Revolution of 1917 and the establishment of the Comintern in 1919, the ‘Catholic International’ was a central papal initiative, which became the ‘largest and most ambitious experiment in cross-border anti-communist mobilization prior to the Cold War’ (p. 5). According to Chamedes, the papacy became a key player in international law through a renovated tool: the bilateral concordat, which often incorporated the 1917 Code of Canon Law, thus integrating ecclesiastical law into the new international order. In the aftermath of World War I, the Vatican began a diplomatic offensive, binding the Church to the new nation-states of Eastern Europe. This diplomacy then proceeded to Central and Western Europe. Drawing on new communication technologies, Catholic internationalists sought to de-privatise religion with a transnational imagined community that involved vying for control of public life in areas such as education and marriage policy. Catholic internationalism fomented a Manichean worldview of Christians versus atheists, and this mindset flourished in interwar Europe. In the new authoritarian states of East-Central Europe, the Fascist conception of organic, corporatist hierarchies helped reinforce the delusion that non-Christians were not true members of the nation, drawing on the residual anti-semitism that was still part of the outlook of many Catholics. Vigorously opposed to the idea of a Communist international order, Catholic internationalists’ idea of socio-political support favoured Fascism as the lesser evil.

The book proceeds chronologically through ten chapters, of which nine focus on the papacies of Benedict xv (1914–22), Pius xi (1922–39) and Pius xii (1939–58). While the epilogue makes brief reference to the renewed anti-Communism of Pope John Paul ii, the book ends largely in the 1960s with the Second Vatican Council (1962–5), when, according to Chamedes, the Vatican gave up its activist diplomatic project of ‘building a specifically Christian international order through legal and cultural activism’ (p. 308).

The overall focus and structure of the book make sense, though the analysis does not create a fully balanced portrait. Chamedes tends to view the papacies of Benedict xv, Pius xi and Pius xii as united by a continuity of aims for international diplomacy. The standpoint of continuity downplays differences between the various popes, as well as separately contextualised episodic shifts. Moments of difference that emerge are complicated by the book's cursory, inconsistent analysis at certain points, such as the contrast between Benedict xv and Pius xii on the issue of international global governance following a world war and particularly the interpretation of Pius xii's acceptance of the United Nations (pp. 232–3, 240–1). On the subject of Catholic-Communist diplomacy, Benedict xv strove to maintain good relations with Soviet Russia, convinced that the fall of Tsarist Orthodoxy was a huge opportunity for missionary outreach to Eastern Europe when the Bolshevik seizure of power was fluid. By contrast, after Soviet hegemony had hardened, Achille Ratti (Pius xi) and Eugenio Pacelli (Pius xii) had more personal experiences of Communist violence (including, in the case of Pacelli, a direct encounter with revolutionaries during the Bavarian Soviet Republic), and were convinced that Communist aggression had to be confronted. Thus, in Chamedes's account, the Vatican often has a monolithic appearance, almost like the Kremlin as written from the perspective of pre-1991 Sovietology, but this was the state of the archival field when the book appeared.

The archival issues demand further investigation. Given the centrality of Eugenio Pacelli (as nuncio, then secretary of state and finally as pope), this is a watershed book that sets out lines of future inquiry. Successfully going beyond ecclesiastical history often unjustly marginalised by non-specialists, the author's stated aim is to ‘bring the Vatican fully within the study of European history’ through the ‘study of the central government of the Roman Catholic Church’ (p. 8). However, the book could not incorporate material from the Vatican archives for the key period of Pius xii, only opened to scholars in 2020. Consequently, the reader lacks analysis of the Vatican's inner struggles during the tenure of the twentieth-century's most controversial pope for the Second World War and the early Cold War. This is not only true for the heated polemics about the ‘silence’ of Pius xii during the Holocaust, but also for other areas of international history relevant for the contemporary world: the post-1945 legacy of anti-semitism (including the formation of the state of Israel), the Vatican's involvement in decolonisation struggles and the continuing crusade against Communism at the height of the Cold War. The victory of Communism (and Liberalism) over Fascism in 1945 presented the Vatican with an awkward historical reckoning.

Given the book's focus on global internationalism and diplomacy regarding Communism, it is surprising that China does not occupy a prominent place in Chamedes's story. The battle for Christian Europe was global, but the book treats the non-European areas superficially. European empires were being reformulated during and after the First World War, with important effects for the era of Vatican II and beyond. Based on events in China in the nexus of missionary empires, Benedict xv's apostolic letter Maximum illud (1919), cited briefly in an endnote (p. 290 n. 85), was a revolutionary moment in modern Catholic history. Among other things, Maximum illud called for non-Europeans to be equal leaders of the Church. Areas of Africa and South-East Asia receive cursory mentions (pp. 286–91), and China gets only a passing reference about Pius xii's 1958 strongly critical encyclical on Communism and the Church in China, Ad apostolorum principis (p. 287). Ending with the era of Pope Francis, the book's epilogue does not mention ongoing Vatican diplomacy with the People's Republic of China over sensitive Church-State issues such as the recognition of Chinese Catholics and the authority of Catholic bishops’ appointments. The Vatican's modern global diplomacy regarding Communism is both a historic event and a contemporary project.

Chamedes has produced a fluidly written, engaging and ground-breaking work that deserves a wide audience. This book will benefit specialists exploring the newly-opened Vatican archives of Pope Pius xii, as well as anyone seeking to understand the role of ideology in modern international history.