In this book, Markus Kornprobst examines a little-discussed subject in international relations, irredentism—“a territorial claim by a sovereign state against another sovereign state, aimed at reaching congruence between the boundaries of the nation and the borders of the state” (p. 9). It excludes purely historical claims (without an ethnic or national component), secession (which is subtraction from a state, whereas irredentism is subtraction from one state and addition to another), or territorial designs for some other reason (oil, for example).

This lack of study is odd given that the impetus for World Wars I and II was based, in part, on irredentist claims (Serbian claims against Bosnia-Herzegovina and German claims against Czechoslovakia and Poland). More recently, the Wars of Yugoslav Succession were driven by irredentist impulses: Belgrade's desire to unite the Serbs in Croatia and Bosnia-Herzegovina were matched by Zagreb's ethnically based claims against Bosnia-Herzegovina. This amounted to the largest and most brutal use of force in Europe since 1945. A less well known instance of irredentism around the same time included Armenia's occupation of the Nagorno-Karabakh region in the Caucasus. Though not reported much in the international media, it resulted in the seizure of one-seventh of Azerbaijan and some one million Azeri refugees. Kornprobst, however, looks at two cases in which the states in question relinquished their irredentist claims without a resort to military means: the Federal Republic of Germany's claims in Eastern Europe (against the German Democratic Republic, Poland, and the Kaliningrad region of the Soviet Union) and Ireland's claims to Northern Ireland.

The central question of Irredentism in European Politics is why these claims were peacefully resolved in favor of the territorial status quo. This puzzle is especially interesting given both the history of irredentist conflicts within Europe and the fact that the irredentist impulse was so deeply held in these societies that they were, in effect, political axioms. Kornprobst's argument is based upon a process of normative change whereby the society in question renounces its irredentist claim (which had powerful normative value) by adopting a new set of values in which the territorial status quo is held to be sacrosanct. This does not mean that the society reimagines itself to exclude their ethnic kin across the border; rather, the identity of the nation remains the same but there is an acceptance of the territorial separation. His argument diverges from the traditional normative literature by focusing more on the domestic processes of change than that inspired from outside, emphasizing the importance of taken-for-granted societal assumptions (which he calls the “repertoire of commonplaces”), identifying the linkages made between established ideas and the advocated idea, and including both constructivist and rationalist mechanisms within the same structure.

In short, Kornprobst makes the case that societies go through three stages of normative change: innovative argumentation (the result of a revolutionary event that forces actors to seek out new ways of looking at and resolving the ethno-territorial conflict); persuasive argumentation (in which actors construct a link between certain taken-for-granted notions and the advocated idea); and, finally, compromise (in which recalcitrant actors seek ways to accept the new normative values that fit with their own worldviews). The most important stage is the second: Only by successfully making the link between the society's deeply held values and the new ideas advocated by the agents of change can the majority's views toward the irredentist claim be replaced by other values. These change agents do so in three ways: through logical reasoning and “inferences made based on general knowledge about cause–effect relationships (abstraction); comparisons that “equate a phenomenon that is already authoritatively interpreted with something that is new and requires interpretation (comparison); and connecting “the advocated idea to existing norms” (comparison) (pp. 39–40).

The argument is largely satisfying, backed by detailed case studies. However, there are some issues of concern. First, the author looks only at positive outcomes—that is, those that went through the process he describes. It would have given the argument greater credibility to have explored cases in which the irredentist claims are more intractable, even if this was done in a shorter format than the German and Irish cases. Why, for example, does a supposedly revolutionary event not lead to innovative argumentation? Or, even if it does, why are change agents unable to successfully link the society's taken-for-granted ideas to the advocated idea? According to the author (p. 231), some situations do not lend themselves to this process, particularly those in which conflict has already been initiated. However, two examples of irredentism in Europe (Serbia and Croatia, the latter of which, somehow, failed to be included in the author's list of irredentist claims in Europe) were preceded by intense debates among elites and the population. In fact, in both cases, multiparty elections were held in which the idea of a Greater Serbia and Greater Croatia was just under the surface. While this book is meant to be theory creating and refining—and therefore a large “n” is not necessarily required—the absence of negative cases looks a little like selecting on the dependent variable.

Second, the argument has a tendency to feel somewhat circular and post hoc. We know that a revolutionary event was enough to “[make] it clear to agents that the old ways of doing things had become obsolete” (p. 5) because it sparked innovative argumentation. But what is the threshold to inspire such change? We only know this by the outcome, not any intrinsic, theoretical understanding of the cause itself. For example, in the German case, the building of the Berlin Wall (1961) was the revolutionary event that started the process. But why was the establishment of the Warsaw Pact (1955) not such an event? One could make the case that the Berlin Wall merely formalized the division between the two Germanys that was well established six years earlier—being in separate, opposing, and nuclear-armed military alliances would seem at first glance to be an event with sufficient impact. Similarly, while the author identifies reasons why some advocacy will likely be more persuasive than others (pp. 44–45), these needed to be fleshed out in such a way that the reason for failure did not appear to be that the change agents either did their job poorly or that insufficient time had gone by in which to convince society of the correctness of their arguments. Seemingly, the primary way in which we understand that persuasive argumentation was successful is because it changed the values of the system, and the reason why it changed these values is because the change agents were successful.

These issues notwithstanding, Kornprobst's book makes a solid contribution concerning why states relinquish irredentist claims. He addresses alternative accounts for the two cases in a convincing way, making a solid argument as to why this process better explains the outcome. His case studies are grounded in solid research that uses appropriate evidence of normative change. Finally, his theoretical chapter is systematic (albeit, somewhat laden with jargon) and includes useful, summarizing tables and charts. In short, this work is highly recommended and will likely serve as the basis for further research into this phenomenon.