Why do small groups of mercenaries sometimes defeat larger armies? Scott Fitzsimmons approaches this question through an examination of mercenary involvement in four African conflicts, testing an argument about the role of cultural norms in shaping military effectiveness and the outcomes of mercenary campaigns. His book is an empirically rich study of dimensions of African history and world politics that have received little serious academic study. The analysis reveals interesting variation in the organizational culture of mercenary groups and connects this to outcomes in ways that have implications for debates about military effectiveness.

Fitzsimmonss’ basic argument is that “a military force’s cultural norms influence its tactical behavior (its military effectiveness), which in turn influences its military performance” (p. 3). Theoretically, the account is influenced by Jeffrey Legro and Elizabeth Kier’s earlier work on military culture, and by Kenneth Pollock’s study of dimensions of Arab military effectiveness. The book elaborates a “normative theory of military performance” (pp. 25–37), according to which armed groups, including state militaries, rebel armies, and mercenary groups, emphasize six basic behavioral norms to varying degrees, namely: creative thinking, decentralized decision making, encouragement of personal initiative, transmission of accurate military information, technical proficiency, and group loyalty. These norms, in turn, shape the military performance of armed groups in ways that affect war outcomes. The small mercenary bands that are militarily effective tend to be relatively good at inculcating these norms within the group and socializing members into the prevailing organizational culture, thus allowing them to defeat materially superior adversaries who cannot encourage these same norms.

This constructivist-inspired, organizational sociology argument is tested against a neorealist alternative, according to which material superiority, in terms of the quantity of military personnel and the quality and quantity of their weapons, explains battlefield outcomes. Neorealism is nothing if not materialist, yet this is a weak alternative explanation that prejudices the outcome of the hypothesis testing. Indeed, international relations theory is relatively poorly equipped to answer the question posed by Fitzsimmons. The offense–defense balance literature on which the book’s neorealist argument draws generates predictions about military competition between great-power armies, not wars waged by a motley crew of child soldiers, shamans, tribal militia, press-ganged peasants, and foreign fighters. In such a context, the neorealist assumption that armies demonstrate “optimal military effectiveness” is particularly problematic: The assumption that leaders make wise decisions in employing military force is difficult even when comparing great-power militaries in World War I; to then assume that disorganized state or rebel militaries make optimal use of technologies and forces is more tenuous still. Moving beyond IR’s paradigm wars to incorporate the insights of recent work on military effectiveness from the narrower security-studies and civil-war literatures would have made for a more compelling theoretical discussion.

The detailed case studies are the key contribution of Mercenaries in Asymmetric Conflicts and merit the attention of other scholars. The author scours the literature on a series of neglected and forgotten campaigns, even tracking down veteran mercenaries to interview in South Africa. These include two conflicts where mercenaries performed well in victory: the Simba Rebellion in Congo (1963–65), where “Mad Mike” Hoare’s “5 Commando” crushed Simba rebels and the Cuban contingent (including Che Guevara) fighting alongside them; and Executive Outcomes’ campaign in Angola (1993–95) that forced The National Union for the Total Independence of Angola (UNITA) back into another doomed peace process. In both cases, remarkably small contingents of mercenaries were crucial to the defeat of more numerous and generally better-armed adversaries. These victories contrast with two cases of poor mercenary performance: “Colonel Callan’s” failed, last-ditch defense of The National Liberation Front of Angola (FNLA) positions at the outset of the Angolan civil war in 1976; and the doomed defense of Mobutu Sese Seko's regime waged by the White Legion, a band of 200 predominantly Serbian and Eastern European mercenaries, in 1997.

Fitzsimmons makes a convincing case that military effectiveness in these conflicts can be traced back to behavioral norms, such as tactical innovation, decentralized decision making, technical proficiency, unit cohesion, and the use of intelligence and information sharing. Militarily effective groups were those that paid close attention to these basic aspects of military organization. Across the author’s four cases, the force with material superiority in terms of numbers of soldiers or available weapons is no match for a materially weaker force that fosters a diverse set of norms that bolster its military effectiveness.

Which of these diverse norms should military leaders emphasize to forge a militarily effective organization in asymmetric warfare? The case studies highlight technical proficiency in advanced weapon systems, particularly air power, and military doctrines such as maneuver warfare and combined arms, which are as much about baseline capabilities (albeit nonmaterial) as they are about norms per se. The role of the armed groups on the same side as the mercenaries also merits further attention. Mercenaries in these cases were employed as front-line shock troops to make up for the inferior capabilities of their client’s military. But their ability to concentrate force at the company or battalion level depended on larger, regular forces holding the line elsewhere and maintaining security in their rear—inversing the roles that most mercenaries in the guise of private security companies play in current conflicts.

Indeed, despite the inherent historical interest of Fitzsimmons’s cases, the book has relatively little to say about contemporary practices and trends in military privatization, most notably in the wars in Iraq and Afghanistan. These more recent, out-of-Africa cases would have made interesting comparison cases, not least in examining the wide variation in organizational cultures among the diverse mercenary and regular forces employed in these wars. But readers curious about the history of mercenary groups in postcolonial Africa, which did much to foster the skepticism of private military companies’ efforts to expand into front-line fighting, are well served by this empirically rich and thoroughly argued book.