Reviewed by: Dominika Kunertova, Universite de MontrealFrom collective action dilemmas to the literature on international crises, scholars have addressed the casse-tete of how to determine an equitable distribution of collective defence costs in the North Atlantic Treaty Organization (NATO). In his new book, Benjamin Zyla offers comprehensive account of the burden-sharing practices of NATO's second-tier powers, such as Canada, Norway, Spain, and the Netherlands, during the first post-Cold War decade (1989-2001). Set in the framework of the changing regional order in Europe, the book evaluates existing burden-sharing measures and contextualizes the burden-sharing behaviour of second-tier power with an emphasis on Canada.Zyla advances two central findings. First, contrary to the expectations of collective action theory, NATO second-tier powers generally shouldered a proportionate share of the Atlantic (8). And second, rather than relying solely on material cost-benefit calculations, Canada acted according to Wolfers' norm of external responsibility, which points to a felt obligation to promote international economic, social, or political conditions to uphold the values of human rights and security, democracy, freedom, and the rule of law (10).[1] To demonstrate his arguments, Zyla broadens burden-sharing criteria to include both military and civilian indicators, and studies domestic preference formation toward NATO and European security governance in Canada. Rooted in liberal international relations (IR) theory, the author conducts an analysis based on explanatory understanding (10) and combines the methods of case study, qualitative content analysis, and semi-structured interviews.Sharing the Burden? is divided into three parts. The first presents the author's theoretical (chapter 2) and conceptual (chapter 3) frameworks for analyzing burden-sharing. Although these two chapters are rich on scholarly debates, Zyla does not always strike reasonable balance. After providing lengthy criticism of realism, followed by defence of liberal IR theory, he dismisses constructivism in single paragraph. Surprisingly, the author does not comment on neoclassical realism, which has recently made contribution to the allied burden-sharing problem in NATO. Furthermore, Zyla squeezes the main neorealist explanation for the absence of free-riding--the abandonment hypothesis--into one footnote (25). Nor is it clear why he omits studies that focus on domestic factors in explaining the contribution dilemma. Taken together, it is odd that at time when IR scholars have been striving to develop more eclectic research, Zyla glorifies liberal IR theory while making straw man out of realism.The second part of the book compares countries' shares of the military burden. Zyla examines NATO member states' participation in the Persian Gulf 1990-1991 and Balkan wars throughout the 1990s (chapters 4 and 5), and introduces the book's most original idea: relative force share index (117). The author claims that instead of comparing absolute allied force contributions, the comparison should be made in relation to national force strength. Finally, in the third part Zyla develops criteria for sharing the civilian burden among NATO's allies. He starts with less quantifiable aspects such as the construction of NATO institutional tools to provide consultation and expertise for Central and Eastern European states, and Canadian support for NATO enlargement policy (chapter 6). Zyla then broadens the burden-sharing discussion by introducing two sets of civilian power indicators, soft military and hard civilian, including national contributions to NATO common budgets and UN peacekeeping operations, or foreign aid (chapter 7).The author could have better explained his choice of military and civilian burden indicators. …