International regimes for the management of inter- and intrastate conflict only work when they can operate in a stable regional security environment. International mediators can have the most skillful negotiators, the most credible “honest-brokers,” the most attractive incentives for peaceful reconciliation, and the most sophisticated political institutions for power sharing, but they are unlikely to succeed without the determined support of Great Powers and so long as there are other powerful actors in the region who encourage one side or the other to resort to violence. Moreover, this is an enduring feature of international relations; it was as true during the Interwar Period as it is now that the Cold War has ended. Security is a nested condition that policymakers and diplomats create from the outside in and not from the inside out.

Erin Jenne makes this argument about the prospects for conflict management using a succession of case studies drawn from European experience in the twentieth century. She also provides a spirited defense for the relevance of Europe for other parts of the world. Europe has a long history of domestic conflict that pits rebellious minorities (linguistic, ethnic, religious, ideological) against oppressive majorities. Europe also has a long history of experimentation in the development of principles and institutions for conflict management, starting with the Peace of Westphalia and extending through the Congress system right up to the present. That process culminated first in the League of Nations and again in the Organization for Cooperation and Security in Europe (OCSE). Finally, Europeans invest in a lot in collective security and peaceful reconciliation by using the promise of acceptance in (or accession to) the club of wealthy nations to create powerful incentives. Europeans also benefit from considerable U.S. support. Hence, Europe offers the most propitious conditions for successful conflict mediation; when such mediation fails, analysts should pay attention to what went wrong.

Jenne’s analysis is rigorous and her argument is convincing. She takes cases from the Interwar Period and from the post—Cold War and compares them to great effect. What she reveals are successes and failures in both historical contexts. Moreover, this variation is as apparent in terms of preventative diplomacy as in terms of postconflict devolution—which is to say, whether we focus on the role of mediators or on the (changing) structure of domestic institutions. In virtually every case, the wider security environment is determinant.

The measure of success used is also important. The goal is not to replace conflict with peace but rather to take steps to reduce tensions between parties to the conflict. Hence, the bulk of Jenne’s work lies in detailed process tracing and cautious judgments about how to interpret the evidence collected. The penultimate chapter tries to generalize the argument using statistical analysis of large-n data sets. The results are less than compelling. This does not detract from the analysis so much as confirm the author’s original choice of technique. If there is a problem, it is more likely to be found in the data, the model, or the estimation technique than in the argument that she is making.

Where Jenne falls short, perhaps, is in developing the implications of her claims. She focuses on the balance of attention in conflict mediation. If policymakers accept her argument, then they should give priority to stabilizing the regional context before investing heavily in in-country conflict mediation. They should ensure that a powerful actor (in the hard security sense) is ready to back up the actions of any third-party mediator or security organization. That is fair enough, and yet there is much more to the argument than this suggests.

Nested Security explains why Peter Gourevitch’s “Second Image Reversed” (“The Second Image Reversed: The International Sources of Domestic Politics,” International Organization 32 [no. 4, 1978]: 881–912) remains central to any analysis of weak, small, or fragile states. That perspective is vital not just to an understanding of peripheral conflicts in Central and East European countries but also to the stabilization of Italy after fascism and the reconciliation of Germany, Poland, and the Czech Republic after German unification. Moreover, Jenne’s analysis suggests, the international security environment rarely pivots around a single all-powerful actor. Instead, it operates like an upside-down version of Robert Putnam’s “Two-Level Games” (“Diplomacy and Domestic Politics: The Logic of Two-Level Games,” International Organization 42 [no. 3, 1988]: 427–460). First the Great Powers have to negotiate a settlement in terms of spheres of influence or shared rules, norms, and conventions, and then they can go to work to eliminate or mediate conflicts at ever-lower levels of aggregation. Since the legitimacy of domestic settlements is often fragile in the face of identity-based political mobilization around distributive concerns, any agreement among the Great Powers requires constant maintenance to prevent one party from nurturing conflict in order to weaken the rest.

This need for constant maintenance that Jenne’s argument highlights exposes the limits of Robert Keohane’s vision of an international security arrangement in After Hegemony (1984). The problem is not that the Great Powers within the system will fail to abide by and underwrite the rules of the game; rather, it is that new powers will arise outside of the regime with an interest in nurturing conflict that will undermine Great Power authority. Importantly, these new powers do not have to be “great” themselves in order to succeed. They only require the resources and the connections necessary to undermine a precarious domestic peace settlement.

These “connections” are analytically important insofar as they highlight bonds between groups across countries that are stronger than the bonds between domestic groups and the state. Jenne uses the notion of “kinship” as a placeholder to be filled with religious affiliation, language, or ethnicity. What is important in the argument is that instability is most likely where state boundaries cut across other types of community (real or imagined). This can be very local, as with Swedes living in Finland, Albanians living in Kosovo and Macedonia, and Russians living in the Baltic States. But it is not a stretch to extend the argument to even larger notions of kinship and to connect these more inclusive kinships to larger “regional” security environments or spheres of influence. If you do so, then Jenne’s argument resonates strongly with Samuel Huntington’s Clash of Civilizations (1996)—albeit without creating some of the controversy engendered by that book.

Jenne’s analysis is persuasive not only because it is so well crafted but also because it connects to many of the core arguments in international relations. Moreover, Nested Security is important insofar as it leaves us with a powerful warning. If there are no Great Powers willing to invest in the maintenance of global security arrangements, then even the most sophisticated international regimes and third-party negotiators will not be able to fill that vacuum. All things being equal, domestic conflicts that could otherwise be mediated will fester (and may even escalate). If regional powers seek to gain local advantages by fostering instability in other countries, the situation will be even worse, as conflicts will not only fester but spread. Finally, that dynamic is not limited to the Middle East or Africa; it is a generalizable condition that applies equally to Europe. Hence, the real lesson Jenne draws from the League of Nations and the European Union is that not even very wealthy nations can afford to be complacent. This is a book that should be widely read.