This is an old-fashioned kind of political science book: a qualitative monograph that aims to shed light on a historically interesting and underresearched topic, namely, the relationship between Socialists and Communists in France, Italy, and Spain during the postwar period. It is historically interesting because the relationship between these parties shaped the nature and fate of the Left, as well as the overall political dynamics in these countries. And although there is a huge literature on both socialist and communist parties, not much of it explicitly analyzes the relationship between these parties. In addition, although all European countries developed socialist and communist parties, France, Italy, and Spain were among a subset where both parts of the Left were fairly strong, and so a focus on intraleft relations in these countries also makes sense.

In order to fully understand the relationship between Socialists and Communists in France, Italy and Spain, Enemy Brothers asks three particular questions. First, “how have Socialist and Communist parties changed over time?” Second, “how have relations between the parties varied over time within countries and cross-nationally?” And third, “what explains these variations?” (p. 7). W. Rand Smith builds his answers to these questions around a “critical junctures” approach, examining periods when these parties faced particularly significant challenges and then analyzing their varied responses to them. Smith argues that three factors shaped socialist and communist behavior during these periods. The first was institutional context, which “refers to the arrangements [of] the main governmental and electoral systems” (p. 24), that is, the political rules of the game. The second was party culture, which refers to the “norms, symbols, collective practices, and collective memory” that constitute a party’s identity (pp. 24–25). And the third was leadership, which simply means paying attention to the type of leaders that different parties “favor” and how much power they have within different parties. He argues that together, these factors explain party behavior in general, and why Socialists and Communists have chosen at some times and in some places to become allies and at others to become enemies in particular.

The chapters include case studies of the evolution of socialist and communist parties in France, Italy and Spain (with shorter sections devoted to Portugal and Greece), as well as analyses of party organization and alliances. These treatments are comprehensive and judicious, and for those interested in party behavior and decision making more generally, they make a good case for why and how organization, culture, and leadership matter. What is curiously lacking from the book, however, is any discussion of ideology, which is particularly strange for a study of the Left, where ideas have been the stuff of endless intellectual and physical battles.

Smith implicitly dismisses the relevance of ideas early on by arguing that the two parties’ “traditions derive from the same roots and share a common struggle” (pp. 4–5). Perhaps. But while twentieth-century socialist and communist parties did indeed both share common roots in the nineteenth-century socialist movement, deep ideological rifts began to open up within this movement by the end of that century; by the interwar period, Socialists and Communists in some places were engaged in fratricidal battles over capitalism, democracy, and much else. These profound ideological (and practical) differences are barely mentioned in the book.

Critically, the level of ideological divergence between Socialists and Communists varied significantly over time and among countries, clearly shaping (but not exclusively determining) the relative strength of the different parts of the Left, as well as their ability to compromise and contract alliances. To be fair to Smith, some of these differences might be captured in his “party culture” variable, but the lack of explicit attention paid to variations in ideological positions and traditions across time and space makes the book’s treatment of intraleft relationships less than fully satisfying.

That said, Enemy Brothers should be helpful both to students of the European Left and political parties more generally. In addition to the particular value derived from a study of party organization, culture, and leadership, Smith’s warning (following Nancy Bermeo) that “political scientists must be certain that attention to history precedes attention to theory, or we are bound to make a whole series of errors” (p. 227) is worth repeating.