Thomas Fischer's study of Latin America's role in the League of Nations draws on exhaustive research to reach a sobering conclusion: the League's impact on Latin America was marginal because the European powers leading it never took much interest in the region. The book's title alludes to the widespread hope among Latin American intellectuals, diplomats and politicians that the League would defend their nations' sovereignty against US interference, but Fischer shows that it never became a weapon of the weak. The League had only very limited success in protecting the sovereignty of weaker nations anywhere, but Latin American representatives had particular difficulty gaining traction with their concerns. Nothing illustrates this better than the repeated failure to modify Article 21 of the League's covenants, which guaranteed the continued validity of the Monroe Doctrine.

After an introduction that reviews the scarce literature on the subject and sketches four approaches to interpret the ‘perspectives, the interests, and the actions of Latin American actors in the League of Nations’ (p. 28), Fischer's study follows a mixed chronological and thematic organisation in his six empirical chapters. The first two provide context on the state of Latin America at the end of the First World War and analyse the motivations for Latin American nations to join or shun the League. The next two focus on the role the Latin American representatives played in the League's formal institutional processes, a discussion that highlights a profound lack of influence and traces attempts starting in the late 1920s to remedy that situation through better coordination. The last two chapters illustrate the limits of Latin American influence in the League and the limits of the League's influence in Latin America. The first of those two, and the fifth chapter overall, analyses the continuous debate about the Monroe Doctrine, whose mention in the covenants appeared to violate the founding principles and mission of the League. The sixth chapter illuminates the League's role in mediating two border conflicts that erupted in the early 1930s. The League intervened late and had little impact in a simmering conflict between Bolivia and Paraguay that culminated in the bloody Chaco War. In contrast, its diplomatic efforts helped resolve the conflict between Peru and Colombia over the Amazonian port town of Leticia.

Fischer teases out some subtle but important shifts in the way that the League responded to Latin American demands. In the early years, international power politics dominated the League's position vis-à-vis Latin America. The British and US governments insisted that Mexico's admission to the League be contingent on reparation payments for damages and expropriations that occurred during the Mexican Revolution, and the Mexican government preferred not to join as a result. Argentina withdrew from the founding conference because European powers rebutted its demand that the covenants guarantee unconditional respect for sovereignty and equality in the League's institutions for all member nations. Brazil left in 1926, after the League refused to grant a permanent seat in the governing council in exchange for accepting Germany's inclusion in that body. Thereafter, as Fischer shows convincingly, the League's leading powers gradually adopted a more conciliatory stance to avoid a further exodus – and the remaining Latin American members moved from ad-hoc to formalised cooperation to demonstrate a united front whenever possible.

Fischer is at his best when he traces how the League's interpretation of Article 21, too, shifted in subtle ways. The Latin American nations had always hoped to use the League as a counterweight to the US-dominated Pan-American framework, and they finally saw some modest success after 1928. In the wake of the Pan-American conference in Havana, which had turned into a protest against US intervention in Nicaragua, the League faced a reinvigorated debate about its interpretation of the Monroe Doctrine. Costa Rica's new government, which considered joining the League, formally requested that the League's governing council clarify its stance on the meaning of Article 21. The official answer stated that international arrangements such as the Monroe Doctrine could co-exist with the League's covenants but could not override or contradict them. Latin American interpretations of this response varied widely. There was a sense, however, that the League had at last accepted an active role in Latin America. Fischer goes further to argue that this renewed resistance to US interventionism, expressed openly in Havana and at least suggested in the League's response to the Costa Rican inquiry, added to the momentum for a revision of the Doctrine's interpretation by the US government. The League's new position helped pave the way for the Good Neighbor Policy.

While Fischer deserves great credit for illuminating the history the League's relations with Latin America in rich detail, one could argue that his heavy reliance on the official paper trail – both the League's own and that of governments interacting with the League – exaggerates its role. While Fischer is careful not to make exaggerated claims about the League's impact in the western hemisphere, he could have been more explicit in ranking the factors that explain key events or policy shifts. The chapter on the Monroe Doctrine, for example, recognises domestic resistance to US interventionism as a crucial factor in presidents Hoover and Roosevelt's shift towards the Good Neighbor Policy. In light of powerful factors such as domestic pressure, the onset of the Great Depression and the conflict at the Pan-American Conference in Havana, the League's position would appear to have made little difference. Another example would be the League's diplomatic effort in the conflict over Leticia, which Fischer portrays as significant for the peaceful resolution of the affair. He notes that neither Brazil nor the United States sabotaged the effort, which can be attributed at least in part to League diplomacy, but he cites the assassination of Peru's warmongering president, Sánchez Cerro, in April 1933 as ‘the decisive factor’ (p. 407). Overall, Fischer provides us with a meticulously researched study that confirms the perception of the League of Nations as a largely ineffective institution, even more so in Latin America than elsewhere. The study is significant even if the League was not.