This is an audacious book. Christopher Darnton seeks to understand the conditions under which state rivalries end given the existence of a common foe. The author explores long-term national rivalries in Cold War Latin America, focusing on how Communist threats, particularly through domestic subversion, induced rapprochement between states, such as between Argentina and Brazil (early 1980s), Argentina and Chile (mid-1980s), and Honduras and Nicaragua (early 1960s). After exploring why several International Relations theories fail to account for such developments, Darnton argues that ‘parochial interests’, coming from the military and foreign staffs, in their struggle for fiscal resources, prestige, and power within the state apparatus, had been the greatest stumbling blocks for the achievement of successful rapprochements in Latin America, disrupting presidential attempts to overcome rivalries. The author points out two conditions as sufficient (but not necessary) to subjugate ‘vested interests’ of the state bureaucracy: the existence of a common foe, allowing domestic agencies to take on new ‘missions’; and a context of severe economic constraint, whose consequences (budget cuts) pressure agencies to substitute new for old ‘missions’ for the sake of keeping their relatively privileged positions within the state. Darnton also extends his argument to account for the maintenance of contemporary rivalries between Islamic countries (Algeria and Morocco), suggesting lessons to policy-makers engaged in coordinating multinational alliances against global jihadism.

Despite interesting and thoughtful insights on Latin American history, Darnton's book presents limitations, some of which, I fear, seriously compromise its findings. To begin with, the author treats all rivalries and rapprochements as if they were the same, making encompassing (but problematic) generalisations. For example, the long-lasting geopolitical dispute between Argentina and Brazil, which had crucial impacts on South American development, is treated at the same level as those between medium and small Latin American countries, such as between Peru and Ecuador, or Honduras and Nicaragua. Mutatis mutandis, this is similar to comparing the causes of the First World War with, say, the roots of the Chaco War between Paraguay and Bolivia. Even though the phenomena are presented under the same label (‘rivalry’ and ‘war’, respectively), their scope, actors and consequences are so different that, in fact, they constitute separate issues. This is not to argue that historical comparisons should be avoided, following Michael Oakeshott's dictum that ‘when comparison begins, as a method of generalisation, history ends’, but they ought be undertaken with caution.

Second, although Darnton acknowledges that his model is not the only one capable of accounting for rapprochements, all cases analysed (nine in total) are explained solely by his theory, giving the impression he has jumped too swiftly to his conclusions. It is true Darnton has presented reasons for why realist, constructivist, and liberal approaches do not sufficiently account for rivalry maintenance or termination for each case, but he does that in a rather mechanical and superficial way. At no time does he consider the possibility of complex interaction effects among different variables and hypotheses, to say nothing of potential indeterminacy. On the other hand, when discussing evidence supportive of ‘parochial interests’, Darnton frequently makes inferences that go beyond his sources. In the supposed attempt by Presidents Jânio Quadros and Arturo Frondizi to overcome rivalry between Argentina and Brazil in the early 1960s, he quotes Brazilian cables from Buenos Aires showing how Frondizi's political power was constrained by the military, mainly due to the president's stand on Cuba (pp. 78–80). However, the words of the Brazilian Ambassador do not seem to allow the conclusion that the Argentine military was constraining Frondizi due to ‘parochial interests’. On the contrary, the cables suggest that the main reason was actually ideological issues, largely the strong anti-Communist bias of Argentina's Armed Forces. Another example refers to the presupposition that national leaders genuinely wanted rapprochement, being blocked by ‘vested interests’. Even if it were plausible to assume that ‘leaders might focus on national problems while agencies focus on parochial interest’ (p. 34), this should have been grounded empirically, which was frequently not the case (see, for instance, pages 53, 62, and 68).

Indeed, the book's main limitation seems to be empirical. Darnton has done a tremendous job in collecting primary and secondary sources about different national rivalries. But the bold scope of the study, from Cold War Latin America to contemporary Islamic conflicts, prevented the author from pursuing comprehensive field work. This becomes clear if one analyses the core of the book, the understanding of Argentina-Brazil's rivalry and rapprochement through four presidential summits (1946, 1961, 1972, and 1980). Darnton employs mainly Brazilian diplomatic sources to look into the 1946 and 1961 meetings (as Argentine documents are too thin), and Argentine official sources to analyse the 1972 and 1980 presidential talks (as Brazilian papers are still classified). Although it is important to look at the two sides of the story to make claims, this is not an impediment per se if several conditions are met, particularly if one cross-references different sources to smooth the tendency of diplomatic accounts for partiality. This is why many specialists in Latin American history employ third-country official sources, mainly US documents, to get a broader picture. In fact, Darnton does the same, but he consulted only those US sources published by the Foreign Relations of the United States (FRUS) series, which is insufficient, as FRUS represent a minority of US documents available. Similarly, the author supports several claims grounded solely on policy-makers’ memoirs (see, for instance, the figure on ‘Chilean subversive threat’ based on Augusto Pinochet's accounts, p. 157). Given that autobiographies and memoirs tend to be highly selective and partial in the presentation of facts, they should never be used in isolation to support claims.

To sum up, Darnton's audacity in trying to deal with many different and complex cases of state rivalry and rapprochement in Cold War Latin America constitutes the book's source of both strength and weakness. His book does provide interesting insights, but they should be taken more carefully than Darnton suggests.