One of the principal puzzles generated by the end of the Cold War was the continued existence of NATO. Why, many asked, should the Atlantic Alliance survive when its primary justification, the Soviet threat, had disappeared? Although this question was addressed by a number of scholars in the 1990s and early 2000s, it has not gone away. In some ways, it has only intensified with NATO's expanding membership, from 16 to 28 countries, and its increased involvement in conflicts beyond its members' borders, as exemplified most recently by its leadership of the International Security Assistance Force in Afghanistan.

This book thus represents a timely as well as useful contribution to the scholarly literature on NATO. It differs from most previous works on the subject, however, in at least two important respects. First, it analyzes NATO in comparative perspective, asking not only why the alliance endures but how it differs from other alliances. Second, it reminds us that the puzzle of NATO's persistence predates the end of the Cold War. Since its very first decade, the alliance has been repeatedly racked by crises that, at least at the time, seemed to threaten its very existence. Yet, on each occasion, its members were able to overcome their differences and maintain a high degree of cooperation.

Why NATO Endures offers two complementary explanations for this pattern. The first emphasizes three structural factors: the international distribution of power, the presence or absence of ideological cleavages, and the scope and pace of warfare (p. 120). Here, the argument is that after 1945, bipolarity, the East–West ideological divide, and the heightened speed and destructiveness of war made European alliances more durable, integrated, and broader in scope than their predecessors. These conditions meant that NATO members were freer to express their disagreement but were also much more dependent on one another and had nowhere else to turn for potential alliance partners.

Wallace Thies's second explanation is that in NATO, these structural predispositions have been reinforced by the peculiar external and internal political dynamics of liberal democracies that endow alliances among them with uniquely “strong self-healing tendencies” (p. 19). On the one hand, democracies are inclined to work together in order to share defense burdens and thus free up resources for other social purposes. In addition, leaders need and want the approval of other democracies in order to legitimize their policies in the eyes of the electorate (pp. 294–95). On the other hand, while disagreements are “a normal feature” of alliances of democracies represented by elected officials who must maintain public support and stand for reelection (p. 300), policymaking in democracies is also self-correcting because of political competition and regular turnover in leadership, which provide “opportunities to reexamine old policies and develop new ones” (p. 297).

Thies develops these arguments in two steps. The first part of the book addresses the question of why NATO is different, it and includes chapters on pre-1939 alliances and the origins and development of NATO into the early 1950s. The second part examines the issue concerning why NATO endures primarily through an examination of what actually happened during six major crises that were said to be especially severe or potentially fatal.

To carry out the analysis, Thies offers a useful definition of an alliance crisis as a situation “when one or more of its members are indifferent between (1) leaving the alliance and (2) making the exertions needed to repair whatever rifts have developed within it” (p. 18). One question that immediately arises, however, is whether even a careful study of NATO crises is the most effective vehicle for identifying the reasons for the alliance's persistence. As the author himself acknowledges, “there is no evidence that any member has ever seriously contemplated leaving the Alliance” (p. 17), and only the departure of certain critical members would have necessarily threatened the existence of a multilateral arrangement such as NATO. At the same time, many pre-1939 alliances ended without a major crisis. A focus on crisis behavior and outcomes may divert attention from long-term trends that are more important for determining the fate of an alliance.

Another unanswered question is which of the two explanations of NATO's persistence sheds the most light. The structural factors Thies identifies would seem to go far toward explaining the ability of the allies to overcome their disagreements during the Cold War, as well as to account for many if not all of the differences between NATO and the pre-1939 great-power alliances that were so much more fragile and short-lived. In order to isolate the distinct contribution of NATO's democratic features, more extensive comparisons with other postwar alliances and even within NATO during and after the Cold War would have been helpful.

At first glance, the six crises examined in Chapters 5–7 are promisingly diverse. Two concern NATO's military posture: the crises occasioned by the development of Soviet ballistic missiles in the 1950s and the deployment of NATO intermediate-range nuclear missiles (INF) in the early 1980s. Two address so-called out-of-area issues: the 1956 Suez crisis and the alliance's response to the Soviet invasion Afghanistan. And two cover nonmilitary issues: the disputes over European assistance for the construction of a Soviet gas pipeline in the 1980s and NATO's reaction to the Bosnian civil war the following decade. In addition, the cases studies are thoroughly researched for the most part; even longtime students of the alliance will find much interesting detail.

Despite the careful attention that Thies devotes to defining an alliance crisis, however, he offers no explicit criteria for his case selection. The reader is thus left to ask why he analyzes these particular crises and not others. One consequence of his choices, as suggested here, is the limited ability to compare NATO's internal dynamics before and after the watershed year of 1990, since only one of the six crises occurred after the end of the Cold War. The book devotes just four pages to the flare-up over the Iraq war, and the interlocking tensions occasioned by the end of the Cold War and the simultaneous moves by European members to develop a common foreign and security policy go unmentioned. Likewise, some important Cold War crises, such as the collapse of the planned multilateral nuclear force (MLF) and, perhaps most notably, France's decision to withdraw from NATO's military structures, are not examined.

In addition, NATO experts are likely to take issue with the handling of some of the cases. For example, the discussion of the crisis occasioned by Soviet missile advances conflates two distinct issues: concerns about growing U.S. vulnerability to Soviet nuclear retaliation, which created doubts about America's willingness to use nuclear weapons in defense of Western Europe, and fears in West Germany, which formally joined the alliance in 1955, that NATO would resort too quickly to nuclear weapons in a conflict, resulting in the unnecessary devastation of German territory. The latter section, moreover, devotes insufficient attention to the important shift in NATO military strategy in early 1957 that was critical for assuaging German concerns.

Finally, on a technical level, the book would have benefited from a list of acronyms, and some page numbers in the index are incorrect. These criticisms notwithstanding, Why NATO Endures merits attention from those who wish to deepen their understanding of the alliance's internal dynamics or gain an appreciation of its remarkable longevity.