In late February, Russia’s war against Ukraine entered its fifth year, and a few days later, the United States and Israel launched massive air strikes on Iran. In addition, European and Asian states are now arming up at the fastest rate since the Cold War, and a war between the United States and China over Taiwan remains a real possibility. Against this dark background, it is important to revisit long-standing discussions about how military power should be applied to achieve strategic goals; how to measure and judge military power accurately; and what factors beyond military force may influence the outcome of war.
One excellent contribution to this debate is a recently published book by Phillips Payson O’Brien. In War and Power: Who Wins Wars—and Why, O’Brien, who is a professor of strategic studies at the University of St Andrews in Scotland, reminds us that the outcome of war may indeed be influenced by aspects beyond guns, air power, and the number of soldiers. He argues that a more holistic approach to how military might is usually measured will improve our understanding of who wins wars and why—and potentially even deter states from going to war in the first place.
In late February, Russia’s war against Ukraine entered its fifth year, and a few days later, the United States and Israel launched massive air strikes on Iran. In addition, European and Asian states are now arming up at the fastest rate since the Cold War, and a war between the United States and China over Taiwan remains a real possibility. Against this dark background, it is important to revisit long-standing discussions about how military power should be applied to achieve strategic goals; how to measure and judge military power accurately; and what factors beyond military force may influence the outcome of war.
One excellent contribution to this debate is a recently published book by Phillips Payson O’Brien. In War and Power: Who Wins Wars—and Why, O’Brien, who is a professor of strategic studies at the University of St Andrews in Scotland, reminds us that the outcome of war may indeed be influenced by aspects beyond guns, air power, and the number of soldiers. He argues that a more holistic approach to how military might is usually measured will improve our understanding of who wins wars and why—and potentially even deter states from going to war in the first place.
O’Brien starts the book by examining the false but widespread prediction of a quick Russian victory against Ukraine in 2022. Not only Russian President Vladimir Putin but the vast majority of Western politicians, analysts, and commentators overestimated Russian military power and underestimated that of Ukraine. The book was written and published before the recent U.S.-Israeli strikes on Iran, but given O’Brien’s take on the United States’ attempts at regime change in Iraq and Afghanistan, it is probably fair to assume that he would have advised Washington not to undertake a similarly overconfident endeavor in Iran. The book ends with a stark warning to Beijing and Washington not to start a cataclysmic war based on misperceptions about each other’s military capabilities.
The book engages with the topic of war and power in five main ways.
First, it takes a broad swing at the ineptness of governments, intelligence communities, and academia in assessing military power and predicting the outcome of war. O’Brien notes that due to the complexity of factors involved, wars seldom develop as planned and often go off the rails, lasting much longer than the aggressor anticipates. The author argues that one of the most fundamental problems in the analysis of war is the tendency to focus on battles, with wars unfolding in a much larger and more complex context than single battles or aerial bombing campaigns.
This is of course not new. Prussian military commander Helmuth von Moltke is famously said to have stated in the 1880s that “no plan survives first contact with the enemy.” Moreover, it is widely acknowledged that European military strategy shifted from a focus on battles to a more comprehensive view during the Napoleonic wars, whereas in China, a broad strategic understanding of warfare is evident in classical texts written as long as 2,500 years ago. Nevertheless, as the wars launched by Putin and U.S. President Donald Trump make clear, military planners and decision-makers need to be continuously reminded about the complexity of war.
Second, O’Brien contends that the risk of analytical failure predicting the outcome of war increases if sociopolitical factors such as a state’s political system, leadership, social fabric, and will to fight are omitted from the calculation. He stresses that militaries are products of a state’s total power; a military can only be as strong as the economic and technological resources that underpins it, the political and military leadership that guides it, and the larger society it serves. Scholars have long debated why society matters in determining the success and failure of military might, and the role of strategic culture is well acknowledged. Yet O’Brien is concerned that analytical communities in most countries continue to neglect these variables when assessing military power. This analytical weakness, he writes, is often enhanced by the profession’s love for narrowly designed, battle-focused war games to describe the expected course of a war.
O’Brien also blames the realist school of international relations—and what he considers its fixation on hard power and military factors—for the flawed methodology applied by analysts and academics when they measure military power. The origin of O’Brien’s criticism is that some prominent representatives of the realist school blamed Russia’s invasion of Ukraine on NATO’s supposed threat to Russia and the latter’s need to secure its sphere of influence, some arguing on these pages that it would be useless for Western countries to send weapons to Ukraine. O’Brien is very critical towards what he sees as realism’s tendency to use balance of power theory in such a deterministic manner. Working within the realm of realism and classical geopolitics myself, I nonetheless understand O’Brien’s point. In today’s European security context, it does not make sense to give in to Russia’s demands for an extended sphere of influence, neither from a normative viewpoint nor from a balance of power standpoint.
Nonetheless, the author’s critique of the school of realism in international relations is overly harsh, for several reasons. For one, O’Brien fails to mention that there is an intense discussion among realists about how to measure power, and this debate is easily available in leading academic journals. Furthermore, it is misleading to assert that the entire school of realism neglects domestic politics, leadership, and the non-material aspects of power. Also, despite the shortcomings of only assessing material capabilities measuring military power, it is even riskier to make assumption about power and war based on non-material factors, or the whim of political leaders. Among all the factors informing a state’s ability to wage war, hard power is undoubtedly the most important one. Hard power may be insufficient to win a war, but it is impossible to fight without it.
Third, O’Brien asserts that realism has done such a poor job of defining what a great power is that the concept has largely become meaningless, and he forwards “full-spectrum power” as an alternative concept. He is critical of Western analysts framing contemporary Russia as a great power—and drawing the conclusion that Ukraine, which is not a great power, was inevitably doomed. I fully agree with the author’s assessment that Putin’s Russia is not a great power, let alone a superpower in the same league as the United States and China, despite its vast geographic size and large arsenal of nuclear weapons. Moreover, “full-spectrum power” is certainly a useful measure to outline the whole range of military and other capabilities a state possesses, from hybrid warfare tools to conventional and non-conventional platforms. Nevertheless, instead of introducing new concepts, my advice would be that scholars and analysts alike strive to be more precise in using well-established concepts such as superpower, great power, and second-tier power. It remains analytically important to distinguish between great powers (or superpowers in the case of China and the United States) and secondary powers, with second-tier states still forced to adapt their policies according to the shifting power and interests of the great powers.
A woman and four small children step onto an industrial aircraft, with soldiers wearing camouflage uniforms in the background.
A U.S. Air Force photo shows passengers entering an aircraft during the U.S. withdrawal from Afghanistan on Aug. 24, 2021. Master Sgt. Donald R. Allen/U.S. Air Forces via Getty Images
Fourth, with relevance to the ongoing debacle in Iran, the book takes a particularly hard swing at the United States’ numerous failed attempts at regime change. O’Brien posits that the U.S. invasion of Iraq in 2003 was a strategic catastrophe, with regional chaos and opposition to the United States across the entire Muslim world increasing after the invasion. He considers the 20-year war and regime change effort in Afghanistan an even larger failure, with the U.S.-installed government in Kabul surviving for only for a few hours after the U.S. withdrawal. There is no denying that with the notable exception of Germany and Japan after World War II, the list of successful attempts at regime change and democracy-building is very short. History tells us that it is difficult to win a nation’s hearts and minds through a military attack.
Fifth, the book engages with how to measure the power balance between the United States and China—and the possibility of these two juggernauts going to war based on miscalculations about their respective military power. China and the United States are superpowers—or full-spectrum powers, to use the book’s term—but O’Brien emphasizes and examines their respective strengths and weaknesses beyond defense budgets and the number of weapon platforms; his interest is in what he calls pre-conflict military metrics.
One difference highlighted in the book is the two countries’ different economic models. The United States still has a technological advantage that allows it to produce more advanced weapons. China, as a manufacturing powerhouse, can build them in far greater numbers. In case of war, this may give the United States a short-term advantage, whereas China has the upper hand in a protracted war of attrition.
Another difference examined in the book is their distinct political systems, with O’Brien claiming that U.S. democracy holds an advantage vis-à-vis China’s authoritarian regime in terms of leadership in war. As China’s command and control system arguably is closer to Russia’s than to that of the United States, the author obviously has a point. Russia’s way of war in Ukraine is not a particularly favorable precedent in his regard.
Men wearing identical military uniforms and carrying identical briefcases walk forward in unison.
Chinese military officials arrive in Beijing for the annual meeting of the National People’s Congress on March 8, 2025.Kevin Frayer/Getty Images
O’Brien further argues that Washington has the upper hand in terms of the two nations’ abilities to rally the public around the flag, but he is worried that the growing political instability in the United States—whose society is increasingly divided against itself—may weaken its position. In my view, he underestimates the role of nationalism in China and how the leadership may leverage this to rally the public during war.
The book furthermore debates the discrepancy in terms of war-waging experience. The United States possesses the most experienced military force in the world, whereas China has one of the least experienced ones. In the Pacific theater of World War II, U.S. inexperience did not matter that much fighting Japan, but in modern warfare, with its high-tech multi-domain operations, experience matters a lot. In a war with China, experience definitely gives the United States an important edge, but that advantage may shrink if the war drags on.
O’Brien also addresses the role of the U.S. alliance network in Asia, which not only enhances the U.S. power position but allows U.S. forces to maintain a forward deployment in China’s neighborhood. However, the author expresses concerns that the United States under the Trump administration is undermining this advantage. In a protracted war, China has a massive home advantage vis-à-vis the United States in terms of logistics, and this would of course be an even greater factor if the U.S. alliance network in the region falls apart.
In sum, it appears that U.S. technology, leadership, command and control systems, and experience waging war would contribute to give the United States an advantage versus China—at least in the initial stages of a war, whereas the advantage is more likely to tilt increasingly in China’s favor in a more protracted war. O’Brien’s distinction between battles and wars is quite important in this regard. In contrast to Russia’s yearslong war of attrition in the trenches and towns of Ukraine, a U.S.-China conflict is more likely to be a limited war at sea and thus closer to what O’Brien defines as a battle.
In War and Power, O’Brien engages with a number of crucial issues guiding war and peace. One important takeaway from the complexity of war discussed in the book is that decision-makers should lean on a rich variety of sources and experts before making a final decision to go to war. That this is seldom the case is a troubling issue raised in the book. Leaders rarely have perfect information—not in democracies and certainly not in authoritarian states. O’Brien debates at length the consequences of Putin’s construction of a political system in Russia that only feeds him with information he wants to hear, and the author airs his concerns about similar developments in Beijing and Washington. For this warning alone, the book deserves a wide readership.
