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Book Reviews Concepts and Doctrine Military History

#WavellReviews “Divided Armies: Inequality & Battlefield Performance in Modern War” by Jason Lyall

Experimental Feature: Audio Read Version

Available here from Princeton University Press

Jason Lyall’s “Divided Armies” is a welcome contribution to our perception of war and how it is fought.  Its release could scarcely have been more timely, during a year in which a persistent trend of racial inequality demonstrated its worst excesses and, in reaction to these events, black and other minority rights became front and centre in politics and society.  While it is hardly surprising that such societal divides work through into a country’s armed forces, these most evident of facts are often the most difficult to define, let alone to quantify.  Providing a theoretical framework to study a wealth of empirically claimed, yet poorly understood dynamics on the battlefield, this work succeeds in achieving both.

A simplified, yet mistaken understanding of armies holds that these armed forces are “coherent, standing entities where soldiers are functionally interchangeable”1.  The book’s main contention holds that the ethnic composition of a state’s armed forces will affect their “efficient production of violence” (or the lack thereof) depending on how restrictive or inclusive its (pre-war) socio-political structures are at home.  At its core, the argument goes against the claim that training, drill, and discipline produces a well-oiled military force.  Instead, as Lyall argues, armies are “flawed by design” and “political constructions […] captive to the identity politics that define a political community”2.

Dulce et decorum est?

To study this assertion, the author makes use of a new dataset detailing war and its belligerents since 1800.  Aptly titled Project Mars, this global history of war is to be lauded for its non-Eurocentric focus and move away from a conventional, great power (that is World War) bias3, by not merely focusing on European belligerents but, also, drawing on non-English literature.  This treasure trove of data is then mined to make the case for what Lyall calls the ‘Military Inequality Coefficient’ (MIC).  This measure is “the degree to which ethnic groups within the military enjoy full membership of the political community or, conversely, are subjected to state-directed collective discrimination or repression”4.  Divided between a pre-modern (1800-1917) and modern era (1918-2011), the MIC is quantified on a scale from 0 (perfect equality) to 1 (perfect inequality).

To test this theoretical assertion, the book is divided in nine chapter across four parts and includes two appendixes.  In the Introduction, the author puts forward the theoretical framework as well as initial theoretical evidence for the argument in Chapters 2 to 4.  Part 2, then, takes this theory to war.  Comparing cases of vastly different rates of military inequality in Chapter 5, a modest degree in Chapter 6, and high, yet altogether moderate rates in Chapter 7.  In Part 3, a microlevel case is explored in Chapter 8.  Chapter 9, then, looks to the theory’s generalisability by discussing the out-of-sample case of the Iraqi army’s performance against Islamic State; as well as making suggestions for further research.  Two appendixes (also available online), as well as the bibliography and the index close the book.

Perhaps the greatest value of this work sits in the qualitative exposition on its extensive dataset.  That said, the extensive dataset makes for a strict choice in case studies, the selection of which is not always clear.  What emerges are concrete examples of how divides and cleavages within societies (and their armies) are easily exploited.  At the same time, it is equally true that more coherent and equal forces, even in the case of technological inferiority, may inflict large military costs on a superior, yet divided, foe.  The similarly extensive exposition on the research design and methodology, makes this work stand out as a prime example of an academic treatise on an important topic.  Of course, the theoretical model that is here maintained artificially elevates the importance of military inequality over other explanations for battlefield (under)performance.  Seen in light of this book’s topic, however, that should not be read as an impediment.  The author’s critical treatment of the argument, as well as proposing other explanations, is particularly worthwhile.

An (interethnic) band of brothers  

Soldier beliefs, interethnic trust and intra-ethnic coordination should be understood as the causal mechanism between pre-war practices of exclusion, and wartime ones of mobilisation, as directly reflected in battlefield performance.  The reluctance of marginalised groups, with their own networks within the military, to die for the dominant (ethnic) group further contributes to high amounts of desertion, defection, and the fratricidal violence necessary to avert it.  It is nevertheless a seductive logic, Lyall asserts, to risk the perpetuation of societal divides in the armed forces.  Going against the presumed difficulties of coordination in the provision of public goods and services, this work makes the case for ethnic diversity within (military) organisations most explicit.  Transactions costs in the delivering of military force (p.45) do not weigh up against the detrimental consequences of military inequality.  Indeed, as becomes clear, it is exactly a high MIC that is the “main driver of battlefield performance.”5

The combination of “arrows-on-maps” expositions of particular battles and campaigns, substantiated with in-depth discussion of their course, as well as the statistical comparison between different belligerents, make this work a refreshing read.  “Divided Armies” serves as a reminder of the tangled nature of war running across a variety of structural, systemic, microlevel, as well as societal faults.  By putting forward military inequality as but one, if understudied, driver of battlefield performance, the book provides the theoretical basis for an intuitively grasped characteristic of armed forces around the world today and through history.  Its argument should inform future policymaking, as well serve as a basis to re-examine past wars.

Axel Dessein

Axel Dessein is a doctoral candidate at the Centre for Grand Strategy, King’s College London and a recipient of a 'The Leverhulme Trust' scholarship on vision of a post-Western world order.  He holds a BA/MA in Oriental Languages and Cultures: China, from Ghent University in Belgium.


  1. p.416
  2. p.2
  3. p.23
  4. p.49
  5. p.21

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