War and Power: Who Wins Wars—and Why

by Phillips Payson O'Brien

A bold, revisionist study of modern warfare, showing that military victory is rooted not in large armies and decisive battles, but in the full spectrum of economic, political, and social power

“Stimulating. ... Full of interesting facts and connections.” —Wall Street Journal

For nearly two centuries, international relations have been premised on the idea of the “Great Powers.” As the thinking went, these mighty states—the European empires of the nineteenth century, the United States and the USSR during the Cold War—were uniquely able to exert their influence on the world stage because of their overwhelming military capabilities. But as military historian Phillips Payson O’Brien argues in War and Power, this conception of power fails to capture the more complicated truth about how wars are fought and won. 

Our focus on the importance of large, well-equipped armies and conclusive battles has obscured the foundational forces that underlie military victories and the actual mechanics of successful warfare. O’Brien suggests a new framework of “full-spectrum powers,” taking into account all of the diverse factors that make a state strong—from economic and technological might, to political stability, to the complex logistics needed to maintain forces in the field. 

Drawing on examples ranging from Napoleon’s France to today’s ascendant China, War and Power offers a critical new understanding of what makes a power truly great. It is vital reading in today’s perilous world.

Genres: History, Nonfiction, War, Politics, Military History, Military Fiction, Political Science

259 pages, Kindle Edition

First published August 28, 2025

About the author

Phillips Payson O’Brien is a Professor of Strategic Studies at the University of St. Andrews in Fife, Scotland, where he has taught since 2016. A graduate of Trinity College in Hartford, Connecticut, O'Brien earned a PhD in British and American politics and naval policy before being selected as Cambridge University’s Mellon Research Fellow in American History, and a Drapers Research Fellow at Pembroke College.

Reviews

[Cami l · Rating 2 out of 5]

Key takeaways from this reading:

*Historically, economic power and technological development has trumped the physical size of a state and population. GDP and the purchasing power per capita of a nation can vastly guide war outcomes, which makes sense because a population that's starving isn't going to be at peak performance at the battlefront or at home. The relative resource abundance experienced by Germans in Nazi Germany at the start of WW2 compared to the rest of Europe backs this point.

*Short, decisive wars are a myth. Wars end when either side (and their allies) run out of resources and the battles need to stop so they can recoup. Individual battles cannot determine the outcomes of wars, but rather a complex interplay of a nation's morale, diplomacy and material resources (economic power that can directly be translated to military technology that can be fabricated, adapted and scaled up in production volume if necessary) can help explain outcomes.

*ALLIES matter a lot. Wars are rarely won by single entities acting alone, and rather, coalitions that can compile their resources and work together for a joint end-goal usually can persist through the end of the war. The author not only emphasizes the importance of execution of complex operations and machinery, but also the ability to recover+ maintain morale in a continual cycle and the multifaceted human element of war.

The language in this book was accessible to the average reader, but the organization of the arguments the author made was hard to follow. I felt like I was jumping around from subject to subject or between time periods (yes, warning this is not organized chronologically) and geographically (heavy focus on Europe, US and east Asia war history). The end goal is to relate how this new understanding of economic and technological power relates to the Russian occupation of Ukraine.

[Matthew Englett · Rating 4 out of 5]

This book really provides a different perspective on war. It’s a perspective that ultimately rings true based on a reading of history. I really think about war and international politics in very different terms after reading this book. Our leaders would be wise to read this and start thinking about conflicts from this perspective. It would save our country and the rest of the world lots of blood and treasure.

[MarcosKtulu · Rating 5 out of 5]

Having such a broad-scoped title, it’s a good exercise here to identify this book’s reason, purpose, and approach to the subject in order to achieve its stated goal.

As for the reason, it addresses the failure of military advisers and IR realist experts to properly assess Ukrainian capabilities to repel the Russian invasion in early 2022. Had NATO policymakers known that Russia’s actual force was far below the level it was expected to perform at, material support for the Ukrainian cause might have arrived earlier on. Bent on not repeating the same kind of misjudgment in the event of a hypothetical armed engagement between the US and China over Taiwan, O’Brien sets out to provide some guidelines to determine how state power and military capabilities could influence the possible outcomes of such a clash.

First, raw economic and military power still matters today, but instead of judging it by sheer size and quantity, how this power is used reveals a great deal more about how a protracted war can actually evolve. Thus, war is serious business. It’s a professional, expensive, unpopular, complex, and unpredictable endeavor. It takes a huge amount of resources to fight, as it builds on technology and large expenditure programs. Above all, war is not an end in itself but rather an expression of policy, à la Clausewitz. Therefore, it relies on leadership and human cooperation within a given state and between states. In that way, O’Brien reviews the historical contribution of leadership and cooperation to understanding the interplay of technology, resource allocation, combined operations, logistics, national will, and alliance commitment into a cohesive and coherent strategy. From his point of view, these are affairs somewhat lacking in realist and neorealist theories.

An example is WWI Britain, which willingly acknowledged US ascendancy, secured a deal with Russia to avert war in Central Asia, and ultimately isolated defiant Germany and its weak partners by bringing France and Italy into the Entente. Throughout the conflict, confident in the uncontested edge given by its well-invested naval supremacy—shown by Dreadnought-class battleships—Britain could adapt to the full fledged mobilized needs of total war, as it relentlessly met the increasing demands of industrial land warfare and the new aerial wing. These challenges of modern warfare are serious enough for the author to consider the outcome of wars not as defined by the opening stages in the ever-sought decisive battle characteristic of the so-called Western way of war, but by the capacity of one state to inflict damage on another while minimizing and enduring losses of its own, without losing the will to fight. Precisely that last aspect allowed the Viet Cong and the Mujahideen to achieve their objectives against more advanced foes despite suffering heavier losses.

Speaking of errors, strategic blunders often start as bad decisions from failing to correctly ascertain the odds stacked against in an ensuing war. In that category falls Chamberlain’s mismanagement of the Sudeten crisis. In the same vein, Stalin’s agreement with Hitler seems to have been short-sighted. In the end, the Axis powers made the worst strategic planning of all, given the enemies they were poised to face. In Germany, this was due to Hitler’s clumsy and whimsical meddling in every state matter, sometimes only partially offset by German stubbornness to accept national defeat. In Japan, bad choices came from the stark division between army and navy command. Italy does not even qualify as a power, as demonstrated by its manifest shortcomings in dealing with a humble but determined Greece.

As the greatest industrial power mostly safe from enemy attack, the US had the best conditions for a war of attrition. O’Brien emphasizes America’s powerhouse capacity to outproduce anyone, and the development of several programs which, no matter how costly, provided the means to deliver payloads deep into the enemy’s heart. Four-engine bombers, chief among them the very long-range B-29, initiated the era of air supremacy. Likewise, American control of sea lanes gained back then, was never given up. On the battlefield, military effectiveness obtained from better command and control systems, training, supply chains, and advanced weapons can usually more than make up for occasional numerical handicaps.

The last chapter, applying all this to the exercise of forecasting a US showdown with China, doesn’t come out as clear-cut as expected, as too many variables are involved. However, the attempt is worth the effort, if only for treading this very engaging, thought-provoking, and well-written path through 20th-century lessons in international relations and warfare.

[Lily · Rating 4 out of 5]

In this revisionist exploration of modern warfare, Phillips Payson O’Brien explores how social, economic, and political power helps win wars. Looking at the “Great Powers” of the last two centuries, O’Brien attributes their military successes to their infrastructure and the many elements that keep massive war machines working, rather than to the large armies and decisive battles that dominate military historiography. Making an argument for “full-spectrum powers” that take all of these factors into account, O’Brien explores Napoleonic France to modern China to expand upon this new military history intellectual framework. Packed with detail and historical evidence, readers will definitely appreciate the lengths that O’Brien has gone to support his argument and provide examples for his larger intellectual framework. The book is informative without being dense or unreadable, and all sorts of military history lovers will greatly appreciate the depth of information and connections in this book. The book itself is well-structured and the prose is approachable, so this makes it a great book for expert historians and general readers alike. Well-written, packed with details, and informative, this is a brilliant new military history book from Phillips Payson O’Brien offering a complex and well thought-out framework to use while studying modern warfare.

Thanks to NetGalley and PublicAffairs for the advance copy.

[Massimo Morelli · Rating 4 out of 5]

The book presents an interesting perspective on war and power. It could have been better written, though. There is repetition, and some parts feel rushed while others drag on. The overly superficial explanation of the political background of each conflict is probably due to the need for brevity, but it’s frustrating nonetheless. In any case, I agree with the message—just not with the editing.

[Juan de la Figuera · Rating 5 out of 5]

Extremely interesting review of war and 'great powers' through, mostly the last two centuries. A much needed rehearsal that puts into context the successes and failures of the presumed hegemonic powers. And the clear impact of stupidity/ability in leaders and the lack of prediction capabilities by most of the military and political establishment to predict or even adapt to recent events such as the Ukraine-Russia war make a very worriesome prospect for the near future.

[Ken · Rating 4 out of 5]

The author paints a picture of American weakened dominance, resulting from damaged and destroyed alliances, lack of moral leadership, a deeply polarized society, and a the turn towards a service economy, rather than an economy with a strong industrial and manufacturing base. We are on the road to perdition.

[Remo · Rating 5 out of 5]

4 stars for the average reader, 5 stars for anyone involved in or interested in national security. I made the tactical blunder of listening to this book vs reading it. There were too many passages I wanted to highlight and think about later.

The book presents “a methodology for understanding national power and then what matters when that power is employed in the conduct of war.” Countries (and leaders) need to look at the variables that create power in peace, and how to regenerate and support that power in times of war. Serious strategy must start with a review of national strengths and weaknesses across the economic, technological, political, and social domains, not just order of battle tables. Logistics, the will of the people, and effective allies are also critical factors. The author uses many examples of past wars, and the current Russo-Ukraine war, to support his theses. Initial expectations of a rapid Russian victory in the war are an example of “experts” underestimating systemic and societal factors. O’Brien argues that better analysis of full spectrum power could have helped analysts and leaders anticipate Russia’s failures.

Paraphrasing a bit from the chapter on Allies: Alliances play an outsize role in determining events in war and peace. In peace allies are an asset from which the larger power can benefit (not rule or dominate). Domination can lead to an empire whose sum is less than the makeup of its parts. The Soviet “allies” were really vassal states that were a drain on the USSR; Western allies were mutually supportive and won WWI and II and the cold war, and he claims could win a war in the IndoPacific.
Wars often mutate from the original goals to something much different; political goals at the beginning of the war rarely survive to the end. “Sometimes simply winning the war is the greater end.” When looking at how a war might develop, leaders should look beyond what will happen when armies actually fight (standard war-gaming objectives) and instead look at how armies can continue to operate, be equipped, and regenerate.

Wars often begin because leaders misperceive their own power and that of their adversaries. Battles are not decisive. What matters are the underlying systems which reflect the real balance of power – economy, technology and logistics. Too many are interested in the “decisive battle," but few wars are won quickly or in the manner any of the opponents thought. What matters is outlasting the enemy, ensuring they can’t restock men, material, and will. America won all the battles in Vietnam but couldn’t stop the VC and NVA from regenerating their forces. The first Gulf War is an exception, but since the allied forces called an end to the war after forcing the Iraqis out of Kuwait perhaps it would not have been and exception if they had driven on Baghdad. (See the second gulf war and the ensuing conflict.) The Allied victories in both world wars were more about economic might and production capacity than generalship. He doesn’t cite the US Civil War, but that is another example.

O’Brien applies his argument to the Russia-Ukraine war. He argues that Russia’s failures in Ukraine reflect systemic shortcomings—corruption, rigid command structures, shallow industrial depth, demographic and economic constraints—vis à vis a Ukraine plugged into Western financial, technological, and intelligence networks. The book suggests that similar structural analysis is essential for thinking about a potential US–China conflict, where questions of supply chains, industrial resilience, societal willpower, and alliance architectures will matter more than military size.

[Harry · Rating 4 out of 5]

The prevailing model used by political theorists for understanding international relations is a theory of behaviour called neo-realism: the idea that states act as coherent entities (you can talk about "America" or "Iraq" doing things) and pursue a self-interested path to maximise their relative power over time (not only are "America" and "Iraq" agents in the world, they're cleverly doing what's best for them all the time).

If this sounds an awful lot like the basic assumptions of and fundamental problems with the study of economics and output of economists, you're on the right track.

It's a truism among historians that, for precisely the reasons listed above among others, the output of political theorists is worth markedly less than the paper it's printed on. The technical term—I believe originally from engineering—is "worse than useless". This is for reasons that are self-evident and bone-deep among historians but perhaps not immediately obvious to normal people and clearly not obvious to the political theorists, who—despite having a worse predictive-success ratio than a chimpanzee playing darts—continue busily producing their nonsense assessments and spouting their absurd analyses.

A notable example is that in the lead-up to February 2022 the only people correctly predicting that Ukraine would resist Putin and resist effectively were not political theorists (Foreign Affairs, probably the peak outlet of the political theory establishment at large, predicted a war over in weeks) or defence specialists (General Mark Milley, the most senior officer in the US armed services and principal military advisor to the president, predicted a war over in hours if not minutes), but historians.

O'Brien bridges the gap brilliantly, arguing simultaneously that a focus on extant military assets ("how many tanks have they got?") the constant preoccupation of military professionals, and that a belief in rational independent actors ("what maximises their relative advantage?"), the simplistic focus of political theorists, blinds both to the actual dynamics of power and conflict between states. He grounds his argument in several historical examples, showing how the tools used by political theorists and defence analysts could not predict either the course or the outcomes of the First World War, Second World War, Vietnam War, the Soviet invasion of Afghanistan, or indeed the present war in Ukraine.

It's not exactly gripping reading, but O'Brien's prose is lucid and fast-moving. It's a rare pleasure to see an entire discipline and structure of theory and received wisdom dismantled so unequivocally in such a brief and comprehensive way. In its place, O'Brien posits a tiered theory of mass, structure and leadership that aligns closely with the nuanced and interwoven way historians traditionally come at interpreting the past. Unfortunately, the people who'd need to buy this new theory in order for it to have an operative impact are the same people who seem satisfied with the terrible predictive power of their current analytical tools (Mark Milley kept his job for well over a year after his disastrous policy guidance on Ukraine, for instance); it seems unlikely to have much impact.

[Chad Manske · Rating 4 out of 5]

Phillips Payson O’Brien’s “War and Power: Who Wins Wars—and Why” is a 2025 Public Affairs book arguing that victory depends less on large armies and decisive battles than on the full spectrum of economic, political, social, technological, logistical, and alliance power. That summary sounds like the sort of thesis that could die honorably in a staff-college seminar, but O’Brien gives it teeth. His book is a sustained assault on the most seductive fantasy in strategy: that power can be counted, stacked, and displayed like tanks on parade. The cleverness of War and Power lies in its refusal to be dazzled by battlefield theater. O’Brien treats battles less as verdicts than as X-rays. They reveal the health of a state: its factories, credit, politics, morale, leaders, transport networks, allies, and capacity to absorb punishment without losing coherence. This makes the book bracingly unsentimental. Heroism matters, but only inside systems that can feed, arm, repair, reinforce, adapt, and explain the war to themselves. O’Brien’s revisionism is especially useful because it punctures both barracks-room determinism and grand-theory abstraction. The “how many divisions?” question is not wrong; it is merely juvenile when asked alone. Likewise, clever geopolitical maps cannot substitute for munitions production, sealift, corruption levels, social trust, or a leader’s capacity for self-deception. War, in O’Brien’s hands, becomes a brutal audit of national competence. The book’s weakness is the shadow side of its strength. Once one accepts the framework, some examples can feel conscripted into the argument rather than discovered by it. O’Brien occasionally risks making “full-spectrum power” so capacious that it explains almost everything, which means it can threaten to explain too much. Still, this is a sharp, timely, and usefully irritating book. It will annoy anyone who wants war reduced to arrows on a map or platforms in a spreadsheet. Good. O’Brien reminds us that nations do not win wars with armies alone. They win, or lose, with the societies that built them. For planners, it is less comfort reading than an unusually useful intellectual field-expedient.

[Coralia M · Rating 5 out of 5]

This book had a different take on how wars are won.
There is no such thing as a short, decisive war. The war is not decided in the battlefield, but the battlefield reveals the state of the powers involved.

The first part focuses on power, detailing all the factors that play a role in the the way wars develop:
- economic/technological strength: make the most advanced stuff, in substantial quantities, at a cost that is sustainable and competitive
- leadership: power can be very personal. It can be erratic and selfish, it can be destructive or far-sighted. One this it is not is consistent
- society and structure: whether the population beliefs in the outcomes of the war and is willing to suffer and make sacrifices for it
- constructing a military: which is a product of the economical/technological resources that underpin it and the leadership choices when it was built. Training plays a key role in how the military performs
- allies: wars are not won on your own. It always comes down to the allies you have, how well communication is going between them and how aligned the underlying goals are. Look at an ally as an asset from which one can benefit, not as a smaller state or people it wants to rule

Second part is focused on war. For me it was a bit harder to read, as my knowledge on wars is quite limited, but it was a good refresher of key moments since WWI to today’s world. I found it insightful how he linked all this history to today’s war situation in Ukraine and the potential conflict in the Indo-Pacific, when two powers with similar caliber (though different strengths in different areas) might face each other. This has not been the case since WWII

[Riada · Rating 4 out of 5]

I went into this book convinced it wasn’t for me. I don’t usually enjoy nonfiction, and I’ve always thought history wasn’t my territory. This book challenged both assumptions, mainly through how clearly it explains the concept of power and war rather than simply recounting events.

What stood out was the way the author breaks down the great power concept and shows how wars are shaped by long-term structures, leadership, and limits, not just battlefield strength. Seeing different conflicts connected through the same underlying patterns gave me a new way of understanding history, and that perspective felt genuinely fresh.

It’s not always an easy read. The pacing can be heavy, and I sometimes had to slow down to keep up, which comes with the territory of nonfiction and historical analysis. Still, the arguments are clear enough that the effort feels worthwhile.

This book didn’t turn me into a nonfiction devotee, but it did change how I think about war and power, and that makes it a read I’m glad I picked up.

[Harald G. · Rating 3 out of 5]

A collection of revealing facts and stories from (mostly) 20th century military history explaining how wars usually are being won. The author, a strategic studies professor, argue that the (currently) most popular theory of international relations - "realism" - do not account for the importance of durable alliances, morale and will to fight. He argues that the importance of great power status, individual battles are overrated. Economic production capacity and alliances lead to the Allies victory in WW2.
The book is an unconcealed criticism of MAGA foreign policy which discard the importance of alliances.

For readers familiar with the international history of the world wars and the Cold war, the conclusions are hardly surprising. Retelling the buildup to the outbreak of WW1 seem to be standard in all Grand strategy books. If you need to quarrel with supporters of the "Mearsheimer school" of international relations, this book is book is an excellent reservoir of counter examples to this theory. Readers interested in military history will already be familiar to many of the stories in this book.

[Paul · Rating 4 out of 5]

Editorial note: Page 70 Change USS Jacinto to USS San Jacinto named after the decisive battle of the War for Texas Independence.
Donald Trump should have read this book before he launched his attack on Iran, before he alienated most of our allies, and before he tried to play 3-card Monte with Zelenskyy using only two cards.
O’Brien takes a broad historical view of the elements of national power and their impact on success or failure in war. He wrote this as an analysis of what ifs or what could be in a struggle between the U.S. and China before our current debacle with Iran. If converted into a check list of does and don’ts, since the end of the Cold War, the U.S. seems to have hit the majority of the don’ts with the current administration doubling down on them.

[Brian · Rating 4 out of 5]

This book lays waste to the assumption that large, technologically advanced powers will win wars quickly - or necessarily at all.

O’Brien argues convincingly that what actually determines military success goes well beyond raw firepower at the start of a conflict. Leadership, the commitment of a nation’s people, the ability to regenerate and adapt, and the quality of allies all matter far more than most analysts acknowledge.

It is an engaging and well written book that gave me a genuine understanding of why wars are rarely ever won quickly - despite promises by politicians - and how they are eventually won and lost.

[David Pancost · Rating 5 out of 5]

Excellent Explanation of What Makes for a Great Power

O'Brien looks at history to develop a framework for analyzing the capacity for a country to to wage war successfully, and uses that framework to explain how 20th and 21st century wars have been won and lost. In the last chapter he uses it to analyze the relative abilities of China and the US to win a Pacific war. This book has been widely cited in discussions of US foreign and defense policy. More than worth your time in understanding both and making sense of what Trump's doing in the Middle East.

[Hugh Carr · Rating 4 out of 5]

I really enjoy Phillips substack writings, & he is the one person that has educated me the most about what is going on in the Ukraine war, & how things might play out. But I would have preferred a much more slimmed down edition, it was just too detailed for me.
But anyone who enjoys military history will love it. I read 90 pages & didn't feel up to finishing it (368 pages) . Maybe I'll finish it another time, I just need to read a lighter subject at the moment 😄

[Chris Barsanti · Rating 4 out of 5]

Fascinatingly counterintuitive, especially in the deemphasis of battles. O’Brien makes a convincing argument that what ultimately means the most in warfare is not the dramatic clashes of arms but more esoteric and mundane factors like industrial production, social cohesion, and the ability to execute complex operations.

[Max · Rating 4 out of 5]

Provided a good basis for a deeper understanding of recent conflicts such as the Ukraine-Russia war. The structure of the book felt a bit odd - the first part of the book was centred on the theme of 'power' and the second part on the theme of 'war', but I didn't feel there was enough of a thematic shift between the two sections to justify this structure.

[Vishal Balani · Rating 3 out of 5]

offers a provocative reevaluation of war, arguing that leadership, society, and alliances often matter more than sheer military might. It is challenging to follow in some places, but the inclusion of historical examples and timely relevance makes it worth reading.

[Eric Smith · Rating 5 out of 5]

An excellent follow-up to the author's work on WWII. Takes the lessons from that conflict about the key importance of force regeneration and generalises them effectively. Of particular importance to any realistic analysis of the power in our present day world.

[Timothy Haggerty · Rating 5 out of 5]

Excellent book

While the subject is timeless and covered a great period of conflict. I still learned things I didn't know and new ways of looking at situations that I hadn't considered. Which is always the mark of an excellent book. I highly recommend this work.

[David Scott · Rating 4 out of 5]

Presenting different thoughts around strategies that will win a war in the 21st century. The author builds a strong essay and polishes it with a conclusion to describe the outcome of potential conflicts between China and America.

[Jonihh · Rating 1 out of 5]

Too much jumping from a subject to another. Also, what is the deal with em dashes? Felt like AI written content.

[Marty · Rating 5 out of 5]

excellent.

[3thn · Rating 5 out of 5]

Fun fun

[LRKK · Rating 5 out of 5]

A well thought out analysis that brings a much-needed systemic perspective to warfare.

[Brendan Quinn]

Audible audiobook

[Kurt · Rating 4 out of 5]

Discusses WW1/WW2 almost exclusively (absolutely does touch on Soviets in Afghanistan and US in Vietnam).

Vietnam is a good case study in what the NV do on this list to win? Sure they had an amount of Soviet backing, but why no focus on the leadership or will of the people. Only discussed in the sense that the US sucked itself into a non willing partnership and how it lost.

Phillips makes great arguments to support his hypothesis; well researched and explained. After reading I feel like it's very difficult to argue against it. This is the sum of all War and Power knowledge!

It focuses, weakly I would say, on a future war between China and the US that was perhaps added as a request. It's a whole lot of crystal balling and it's hard to know if it's too conservative - I think so, but that might be a lack of subject expertise rather than knowledgeable conclusion. Geopolitics is changing so fast in 2025 it's hard to put anything to paper and be confident - the book already has an epilogue updating it at point of printing!

Overall I learned a lot about WW1, WW2 and the specific concepts discussed; and it was enjoyable. I feel confident speaking to the concepts and promoting the idea Philips is discussing.