The relationship between India and Pakistan represents one of the most enduring and significant international rivalries over the last century. Almost from the very moment of independence from colonial rule in 1947, the two states have engaged in fractious relations, which have run the gamut from outright war to escalatory standoffs to strained coexistence to hesitant periods of rapprochement. Christopher Clary, in a refreshing new book on the 75-year Indo–Pakistan relationship in the broader context of rivalries in international relations, focuses on the politics of foreign policymaking internal to states to account for the remarkable variation in the relations between India and Pakistan over time.

Such an account is important both theoretically and substantively. There have been heightened recent efforts to “decouple” the two countries in public discourse, largely by those who want to highlight India as an emergent global power that should be considered a serious competitor to China and a potential ally of the United States, while characterizing Pakistan as simply a failed state and thus a distraction or spoiler. This framing elides the importance of India and Pakistan to one another in concrete national security terms and how much the two countries’ relations may be a product of what is similar among them, rather than what is different between them. Theoretically, the rivalrous relationship between India and Pakistan represents a case that maximizes variation on the dependent variable, given that, as Clary shows throughout the book, the relationship has changed significantly even though structural factors have remained relatively constant. Previous research on South Asia and with other rivalries have tended to focus on certain periods, such as that of the Cold War, in effect privileging influences that are native to that period. The long duration of the India–Pakistan rivalry allows us to examine variation over time while keeping the same actors constant, rather than picking signal from noise in a messy universe of dyad-years.

To explain variation in the relationship and movements of escalation to war and rapprochement toward conciliation, Clary introduces “leader primacy theory.” He argues that strategic incentives for greater cooperation are necessary but by themselves insufficient for directions toward peace. Rather, national leadership must create and sustain a “concentration of foreign policy authority” (30) in which leaders must first consolidate power to effectuate policy change. Escalation toward conflict, by contrast, requires only shifts in strategic incentives—“when the costs of war today are less than continuing the status quo” (30)—and can occur in contexts of fragmented foreign policy authority. In general, “fractured foreign policy favors continued rivalry” (32) because maintaining the status quo requires the assent of fewer veto players, and weak leaders fear being undermined by policy hawks through stalling, sabotage, or information distortion. Clary’s title, The Difficult Politics of Peace, is therefore apt: rapprochement is difficult because the national leaders of rival states require both the incentives to reach out to one another and the capacity to bend foreign policy authority to their will. It represents a challenging but not impossible set of circumstances and thus explains key cases of rapprochement, as well as those of stasis and escalation, in the fractious 75 years of relations between India and Pakistan.

In testing whether leader primacy theory, in relation to alternative explanations, accounts for variations in the relationship between the two countries, Clary presents a rich diplomatic and elite political history, based on primary sources from declassified documents, archives, and interviews with former diplomats and policy makers, as well as a deep critical reading of extant accounts. Any reader wishing to know details of the origins and trajectory of this important bilateral rivalry in an accessible and engaging fashion would learn much from this history. Negotiations on and confrontations over Kashmir in the first three decades are especially well covered. Clary’s book strikes an effective balance between providing an empirical account while regularly referring to theoretical frameworks, which is rare in a field populated by both historians and social scientists.

Cary’s fidelity to primary sources and accounts, however, creates a necessary but still unfortunate imbalance in coverage: less than one-third of the book covers the period since 1977. The historical record is certainly much fuller for the period between 1947 and 1977, and political sensitivities have faded, such that theories can be tested with better evidence. However, this implicitly leads to a historiography of continuity rather than change in the ways that the rivalry is conducted in the latter period. Three aspects of disjuncture over recent decades suggest themselves, which might at least add nuance to the dynamics and import of leader primacy; these are ably covered in the book and are the subject of significant scholarship, but they are seamlessly incorporated into the overall narrative, rather than treated as turning points. The first is Pakistan’s strategic use of proxies in the early 1990s: insurgent groups mobilized from within Indian Kashmir that could strike military and security forces targets in the state and conduct terrorist attacks in locations like Delhi and Mumbai, while maintaining (often implausible) deniability. This meant that, at least between the 1990s and 2010s, there was a significant domestic security and political component to India’s relations with Pakistan, which shaped both the incentives facing Indian leadership and the convergent structures of the foreign policy and national security apparatus. The second is India’s and then Pakistan’s nuclear tests in 1998. Much of the international relations scholarship in South Asia has been concerned with the “instability-stability paradox,” or the extent to which the overall strategic stability of nuclear competition might allow greater uncertainty and conflict at substrategic levels; this would not only affect the incentives but also would reduce the capacity to credibly punish and thus deter policy adventurism. Third, in India, there have been substantive qualitative changes in the nature of the regime, with Narendra Modi’s BJP governments since 2014 securing absolute majorities and ruling in a relatively absolute manner. Leader primacy theory would suggest that Modi has fully achieved a dramatic concentration of foreign policy authority and thus might pursue deescalation and rapprochement whenever the incentives are favorable. Deescalation was evident after the Pulwama-Pathankot crisis, but Modi’s hardline majoritarian ideological orientation—complete with Hindu nationalism’s explicitly revisionist principle Akhand Bharat—might suggest that, unlike previous Indian leadership, Modi faces no incentives to negotiate or even engage with Pakistan as an interlocutor. India under Modi is attempting to create a hierarchy of national powers in the region, in effect denying the rivalry. It is perhaps unlikely to succeed given China’s influence, but this strategy is a new one in the relationship.

Clary’s book represents an important theoretical and empirical account of a key case of interstate rivalry; students of South Asia and international relations will benefit greatly from close attention to it.