States use wedge strategies to prevent hostile alliances from forming or to dis­perse those that have formed. These strategies can cause power alignments that are otherwise unlikely to occur, and thus have significant consequences for international politics. How do such strategies work and what conditions promote their success? The wedge strategies that are likely to have significant effects use selective accommodation—concessions, compensations, and other inducements—to detach and neutralize potential adversaries. These kinds of strategies play important roles in the statecraft of both defensive and offensive powers. Defenders use selective accommodation to balance against a primary threat by neutralizing lesser ones that might ally with it. Expansionists use se­lective accommodation to prevent or break up blocking coalitions, isolating opposing states by inducing potential balancers to buck-pass, bandwagon, or hide. Two cases—Great Britain’s defensive attempts to accommodate Italy in the late 1930s and Germany’s offensive efforts to accommodate the Soviet Union in 1939—help to demonstrate these arguments. By paying attention to these dynamics, international relations scholars can better understand how balancing works in specific cases, how it manifests more broadly in interna­tional politics, and why it sometimes fails in situations where it ought to work well.

It is hard to imagine that any British leader in 1940 — let alone Winston Churchill — would venture to appease another Fascist dictator in Europe. But when it came to British relations with Franco's Spain Churchill doggedly pursued a wedge strategy that hinged on offers to reward and accommodate Madrid. And the results were impressive. As Britain faced the Nazi menace alone in 1940–41, Spain's government remained non-belligerent, despite it's ideological affinity and historical debt to the Axis powers, and despite its opportunity to re-claim Gibraltar and parts of Morocco with Nazi help. This surprising outcome was no minor feat, for Spain's non-belligerence in 1940 had enormous implications for the future course and duration of the conflict. The deviant case of Spain in 1940 is thus important not only because leading alliance theories do not explain it, but also because it made a big difference in the biggest war of the 20th century. This article revisits the history of this critical juncture of the war, and sets forth a theoretical framework for understanding the role of wedge strategy in the case, and in international security more generally.

This volume explores whether the emerging norm of intervention has backfired by exacerbating violence in conflicts such as Kosovo, leading to the unnecessary deaths and ethnic cleansing of innocent civilians.