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Edited by Jude Blanchette, formerly Freeman Chair in China Studies at CSIS, and Hal Brands of SAIS, the Marshall Papers is a series of essays that probes and challenges the assessments underpinning the U.S. approach to great power rivalry. The papers are rigorous yet provocative, continually pushing the boundaries of intellectual and policy debates. In this Marshall Paper, Phillips P. O’Brien assesses the critical importance of allies in deciding major conflicts and argues that a potential war between China and the United States in the Indo-Pacific would likely go on for an extended period, with the United States needing to lean on its regional allies for logistical support and for their manufacturing capacities. O’Brien argues that the U.S. allies appear strong on paper, but that they are untested, while China’s allies of Russia and North Korea, though weaker, appear much more willing to contribute serious resources to one another. Therefore, a long conflict may hinge more on commitment than on capability.
The much-beloved great-power paradigm of international relations and the era to which the United States has recently claimed it is returning is deeply flawed on many levels. One of the most basic problems is the attention placed on the supposedly “great” powers themselves—raising them above others and bestowing upon them a potency they rarely possess.
As seen consistently since the Napoleonic Wars, focusing on individual powers overlooks the fact that wars (and even peaceful disputes) are usually won by stronger alliances. It is the grouping of more powerful states that often—one might even say usually—determines international affairs, not the acts of individual states. Indeed, it is arguable that the greatest single powers have regularly been beaten by stronger alliances. The British Empire of the American Revolution was beaten by the American colonists allied to the French, Dutch, and Spanish, for instance. A few decades later, Napoleon, who controlled most of Europe, was defeated by a more powerful alliance of the Russians, British, Austrians, and Prussians.
In the twentieth century, this pattern repeated itself. Germany was arguably the greatest power in Europe in both World Wars, but was defeated twice by superior alliances. At the same time, Germany was held back by poor allies, such as Austria-Hungary in World War I and Fascist Italy in World War II.
The Cold War likewise saw two very different alliances in competition. The United States was allied with the major states of Western Europe, helping to maintain the economic dominance of the West. The USSR was allied with the states of Eastern Europe, whose loyalty it could only maintain through brute force, greatly diminishing their contribution to Soviet strength. In the end, the more powerful NATO alliance emerged to dominate Europe, while the Warsaw Pact was confined to history.
Alliances matter because they affect power relationships in a number of ways. In peacetime, alliances are some of the best deterrents to adversary action—if they are assumed strongly united. Before 1914, wars were often prevented because alliance structures deterred individual powers from initiating major hostilities. In 1907, ironically, it was the assumed strength of the German-Austrian alliance (which, along with Italy, was often called the Central Powers) that deterred Russia from risking an outright war over the control of Bosnia.
When states no longer believe that alliances can deter effectively, however, war can result. In both 1914 and 1939, for instance, different German leaderships—Kaiser Wilhelm II’s in the first instance and Adolf Hitler’s in the second—calculated that the alliances arrayed against Germany were not sufficiently united to prevent a German victory. In 1914, the view was that Britain, in many ways the key member of the Triple alliance (which also included France and Russia) arrayed against Germany, would either not join in any European war or, if it did, would not be able to influence the war before German military power had decided its outcome.
Something similar happened in 1939. At that time, Hitler, worried that an alliance between Britain, France, and the Soviet Union might go to war against him if he invaded Poland, broke up the potential grouping through the Nazi-Soviet Pact with Joseph Stalin. By making Stalin an ally and splintering the prior alliance, Hitler believed he had made his attack on Poland strategically viable.
If strong alliances can deter wars while weak or fractured ones encourage them, then once wars start, the stronger alliance almost always ends up in the superior position. The World Wars are the obvious example: In both World War I and World War II, the Allies—anchored by Britain and the United States in both, and including other significant powers such as France and Russia (and later the Soviet Union)—presented the opponents with such overwhelming combined production capacity and technological advancements that victory was all but inevitable.
Considering the importance of alliances in determining the outcome of international rivalries in both peace and war, it is surprising how often they are overlooked when discussing the Indo-Pacific. Though it is common to discuss any war in the region as revolving around the United States and China and their individual intentions and capabilities, such a conflict would be heavily influenced by the two acting as part of larger alliances or through the support offered by friendly states such as in the case of China. Indeed, just as alliances have played a major role in shaping the course of the Russia-Ukrainian War, it would be safe to say that alliances could very well determine the future of the Indo-Pacific. The war in Ukraine has also revealed that possessing the most advanced military equipment is not enough—the willingness to use it matters even more.
To begin with, the Russia-Ukrainian War has shown that neither Russia nor Ukraine can be seen as powers fighting on their own—and how mistaken early analyses of the war were because they approached the conflict in that light. Before February 24, 2022, it was widely assumed that Russia, as a great power, would overwhelm Ukraine in a “shock and awe” campaign in a matter of days or weeks.
With the war assumed to be so short in duration, the role of allies or supporters was downgraded. Indeed, it was widely assumed that the war would be so short that Ukraine should not be supported by those inclined to do so. It was a view which, sadly, seemed to be widely shared within the Biden administration.
Because of this outlook, Ukraine’s group of possible allies—which were far more economically powerful than Russia’s, with the United States in the lead but also including most of Europe—provided Ukraine with only limited weapons before Russia’s full-scale invasion. Even once the invasion started Ukrainian resistance proved to be far more effective, indicating the war could last much longer, aid to Ukraine was strictly limited in terms of range and capabilities.
Russia’s experience with its allies was in some ways a mirror image. Two of its allies, North Korea and Iran, showed that economic power alone is not enough. Both states provided extremely important military support in mass quantities—and gave it with no strings attached. Iran first provided Russia with Iranian-produced Shahed drones (unmanned aerial vehicles, or UAVs), which proved so effective that Iran later agreed to let Russia produce them domestically. This meant that by the second half of 2024, Shaheds were the most common system used by Russia to attack Ukrainian cities practically every night.
North Korea might even have surpassed such aid. The North Koreans not only provided Russia with more artillery shells than all of Europe and the United States combined had provided to Ukraine, they even ended up sending their own troops to fight (and die) on Russia’s behalf. While Ukraine’s allies seemed to panic at the thought of sending their own troops—even for support work like training Ukrainian soldiers—North Koreans entered the front lines of combat.
So, the innate strength of allies alone matters only so much. The willingness of allies to do what is needed to win can trump statistical power. The result of the war in Ukraine, for instance, is being decided in real-time by the behavior of allies and partners—or those thought to be allies and partners. Russia has received consistent support throughout the war from allies such as Iran and North Korea—and, to a lesser degree, China. They have provided Russia with the weapons they could, and put little or no restrictions on their use. Ukraine has not been so lucky. Though its allies are economically and technologically much stronger than Russia, these allies have been restrictive and unwilling to commit to Ukrainian victory. Indeed, at the time of writing, the United States seems to be in the process of switching from being a supporter of Ukraine to be, at best, a tacit enabler of Russian power. President Trump seems set on acting not as an ally of Ukraine, but as a mediator between the two countries, and appears to be intent on forcing Ukraine to cede some of its territory to Russia without any strong security guarantees. This shift by the United States will almost certainly play a major role in how the war progresses in 2025.
If the overall balance of forces in the Indo-Pacific were presented in chart form, there would be one clearly dominant force and one secondary force. The dominant force would be the U.S.-led alliance. The United States itself remains arguably the most powerful state in the world. It still possesses the strongest and most technologically advanced economy, dominating the high-tech landscape, and is able to build the most advanced weapons in the world. It is home to the world’s most efficient and powerful financial markets and can raise money in vast quantities from across the world.
The United States is not without its flaws. Its ability to manufacture in mass has withered over the previous decades, as it has outsourced much of its finished production processes to Asia, particularly China. However, the United States also has powerful Indo-Pacific Allies who have developed the capacity to manufacture what the United States cannot, and those allies must step up to compensate.
Shipbuilding is a powerful example of these dynamics. Since the end of the Cold War, the U.S. shipbuilding industry has collapsed. The United States now hardly produces any non-warships (and produces relatively few warships, as well), while China has become the world’s largest ship producer by far. Indeed, when compared to the world’s major shipbuilding powers, the United States does not even appear as an independent producer—it is relegated to “other” (see Figure 1).
What stands out, however, is not just the Chinese position, but also how U.S. allies Japan and South Korea occupy second and third place—with a combined shipbuilding capacity that at least matches that of China. And this is just one example of the economic and technological capabilities of U.S. allies in the Indo-Pacific. In fact, if the economies of Japan (fourth-largest in the world) Australia (thirteenth), South Korea (fourteenth), and Taiwan (approximately twentieth) were combined, you would have an economy that would easily be the third-most powerful in the world.1 Such a power would also have world-leading capabilities, such as Taiwan’s semiconductor production capacity, and a highly developed ability to make arms, such as South Korea’s ammunition manufacturing.2
And this does not include other U.S. allies in the area such as the Philippines, Singapore, and Thailand. What is more, both Vietnam and India currently have or have had border wars with China—and neither is particularly well-disposed toward the Beijing government.
All together, the possible pool of U.S. allies or U.S.-inclined powers in the Indo-Pacific is a powerful and diverse coalition—with economic strength and a combined military power of some heft. Of course, just adding them together in theory is meaningless. They would need an alliance structure under which to coordinate their actions and take advantage of all that potential power. Only the United States could provide that—but if it does not, all that is really left is a list of wealthy nations who have no ability to act as an alliance.
The list of possible Chinese partners (China does not have any formal allies) is far less impressive in material terms. Indeed, China has so antagonized many of the countries on its borders that its two closest allies are as much dependencies as anything else—Russia and North Korea. The Russian economy is about tenth in the world, though reliant on resource extraction as much as anything else, and with limited technological capacity for manufacturing advanced equipment (the war in Ukraine has once again exposed how much less effective Russian weapons are than U.S. weapons).
Of course, compared to North Korea, Russia is an economic titan. North Korea is one of the most economically backward places in the world, with a population that regularly experiences government-caused famine and deprivation. Calculating the accurate size of the North Korean economy is not easy as it is such a closed society. However, the CIA recently estimated that North Korea had the 138th-largest economy in the world—and was only the 201st-fastest-growing economy.3
If China’s two most dependent partners are economically backward compared to U.S. allies, they have certain advantages for China that U.S. allies lack in terms of willingness to commit. North Korea has already revealed in the war in Ukrainian that they will do almost anything to win a war and will provide aid to their allies without much hesitation and fundamentally without limits. Both Russia and North Korea are heavily militarized powers with large, if not terribly efficient, militaries. North Korea has a mass force of over a million armed soldiers (though those who have fought in Russia have shown very limited tactical sense).
The Russian military is considerably more powerful than the North Korean military, though it was also revealed to be seriously overrated and has suffered major losses in the war against Ukraine. It has certain high-quality ranged weapons and has learned some lessons about modern warfare (in particular, how to fight in a UAV-rich environment).
What these allies could do in case of war would be to offer useful support in a few areas. Both, but particularly Russia, could provide large amounts of raw materials to keep the Chinese economy producing at maximum output and to keep the Chinese population fed. They could also tie down the forces of the United States and its allies through demonstrations and actions from the demilitarized zone on the Korean Peninsula all the way to the Arctic, Europe, and the Middle East.
Such military demonstrations could be very useful. If the North Koreans could distract both South Korean and Japanese forces, it would lessen the kinds of forces that U.S. allies (if they were so inclined) could send to help Taiwan. North Korea could do that even without a direct ground attack, by launching or even threatening to launch a large missile and ranged weapons campaign. It should be noted that the North Koreans are, after a rocky start, gaining important experience in UAV warfare through their deployments in Russia. Russia, on the other hand, could lessen the chance of any wide-scale European support for Taiwan or other democratic Asian allies. As it is, European states have precious few resources that they could deploy to the Pacific, and they would hardly want to spare them if the Russians were threatening.
Thus, China’s allies could help force the United States to fight with more limited aid from its allies, even without resorting to full-scale war.
China’s allies are both economically and technologically much weaker than the United States’, but at the same time, they seem more politically willing to support Chinese interests. This difference is of considerable importance. Though the United States may have allies in the Indo-Pacific, it is not acting as the leader of a powerful alliance.
This is because not all of the United States’ allies are pledged, or even inclined, to fight for each other—and as such, can play only a limited role in deterring China from action, if the Chinese government was so inclined. That basic problem can be seen by looking at the two most likely flashpoints that could, at any time, go into crisis mode for the United States and China—the South China Sea or the fate of Taiwan.
These are two of the most well-known and contested areas of the globe. The South China Sea is a constant flashpoint between the United States, China, and a number of U.S. allies or close friends (see Figure 2). China’s government claims control over the waters of the area through what is referred to as its “nine-dash line” claim. Though the claim has been ruled to be without merit by an international court of arbitration, this has not stopped Beijing from building up and fortifying a chain of island bases, many of them artificial constructions, in the area.4 The country is now regularly deploying powerful naval assets to assert their claim to the waters, in particular assaulting, often with water cannons, Philippine civilian and military vessels. It should also be mentioned that Taiwan sits within the nine-dash line.
The United States has a long-standing defense treaty with the Philippines, one which was updated in 2023 to reflect Philippine concerns over the South China Sea.5 The United States has also used firm rhetoric to say that it will defend the Philippines if the moment comes, in an attempt to deter China. However, the reality is that this deterrence seems only sporadically successful at best. For the past two years, the two states have seen a series of clashes as they each seek to stake their claims to access and control the eastern parts of the South China Sea. In August 2024, for instance, Chinese and Philippine warships clashed near the Sabina Shoal, which saw vessels from both sides crashing into each other.6
Chinese assertiveness in the region and willingness to risk military clashes seems at least partly motivated by the fact that, outside of the United States, it is not clear that any other state is committed to the defense of the Philippines’ rights. While Japan sells military equipment to the Philippines, for instance, it is not committed to its defense. And if Japan is not committed, the idea of other U.S. allies, such as South Korea or Australia, committing themselves is decidedly unlikely.
Things are not much better when it comes to the unity of U.S. allies when it comes to their ability to deter China over Taiwan. The air and waters around Taiwan are some of the most heavily militarized in the world. Over the last few years, the Chinese have run a continual series of exercises and patrols, at least 10 major ones since 2018, to say nothing of the practically continuous Chinese naval and air activity around Taiwan. This looks to be a clear attempt to intimidate the Taiwan people.7
Considering the vital strategic importance of Taiwan—geographically, economically, and arguably militarily—one might think that U.S. allies in the region would be willing to commit to its defense. However, once again showing the unstable nature of the U.S. alliance grouping, few, if any, actually are. Once again, Japan would be a vital strategic power in the defense of Taiwan, and a clear Japanese commitment to stand side-by-side with the United States could be a powerful deterrent.8
However, Japan has been reluctant to make such a move. Though Japan is increasing defense spending considerably (from an admittedly low base) and claiming that it will play a more assertive role in the world, Japanese leadership, in a position it has maintained for decades, has also been careful not to say it will fight for Taiwan—even if the United States eventually decides that it will.9 In the 2022 National Security Strategy of Japan, the Japanese government speaks warmly of relations with Taiwan and acknowledges the island’s strategic importance but remains entirely ambiguous on whether Japan would fight for Taiwanese independence:
Japan’s relationship with Taiwan has been maintained as a non-governmental working relationship based on the Japan-China Joint Communique in 1972. Japan’s basic position regarding Taiwan remains unchanged. Taiwan is an extremely important partner and a precious friend of Japan, with whom Japan shares fundamental values, including democracy, and has close economic and personal ties. Peace and stability across the Taiwan Strait is an indispensable element for the security and prosperity of the international community, and Japan will continue to make various efforts based on its position that the cross-strait issues are expected to be resolved peacefully.10
If Japan is hedging on this issue, other U.S. allies are more active in saying that they will not fight for Taiwan. Australia might be the best example. Much has been made of Australia’s role as a U.S. ally—to such a degree that, in 2021, Australia reneged on a deal to build submarines with France in favor of a similar agreement with the United States and Britain under what is known as the AUKUS agreement.11
The United States and Australia are allies through the ANZUS Treaty (which originally included New Zealand), signed in 1951. The treaty has led to long-term integration between the U.S. and Australian militaries, and Australians have fought alongside the United States in conflicts around the world, from Vietnam to Iraq and Afghanistan. However, the Australian government has also gone out of its way to say that it is not committed to fighting for Taiwan—even if the United States eventually does. In 2023, Australian Deputy Prime Minister Richard Marles stated categorically that Australia had “absolutely not” pledged itself to the defense of Taiwan under AUKUS.12
This is the basic problem and contrast between U.S. allies and China’s alliances. U.S. allies are held together by individual ties with the United States. If they could act together, they could be an extremely powerful deterrent. However, as of now, they are really a series of unconnected bilateral security relationships—far from being mutually supportive. Indeed, this fragmented structure adds a layer of confusion to U.S. planning, as the United States cannot be sure who would fight for what.
The list of possible Chinese partners, on the other hand, is intrinsically not nearly as powerful. However, its allies have shown a willingness to go to war for each other and provide as much weaponry as possible without limitations. It is, therefore, more a question of the size of the dog in the fight versus the size of the fight in the dog.
This level of commitment from U.S. and Chinese allies (or lack thereof) could go a long way to deciding the outcome of a U.S.-China war in the Indo-Pacific. There are many different scenarios that one could devise for the region, and listing them makes little sense. What is practical is to think in terms of a short war versus a long war—with a greater emphasis on the latter.
Too often, analysts and others are drawn in by what is best called the “short-war myth”—the idea that a war will resemble the conflict drawn up by prewar planners and be decided by engagements in its opening phases. This idea, that a war “will be over by Christmas” appears regularly from World War I, where Germany hoped to win in a short opening campaign, to the present Russia-Ukrainian War, which many confidently predicted would see Russia conquer most of Ukraine in weeks or even days.
One of the only benefits of the terrible war in Ukraine is that it seems to have injected discussions of a U.S.-China war in the Indo-Pacific with a greater awareness that the opening stages might not be decisive. Before February 24, 2022, there was discussion of a war between the United States and China over Taiwan being over relatively quickly—often with a quick Chinese victory. In October 2020, the Pentagon ran a series of war games simulating a U.S. attempt to defend Taiwan, and reportedly, the United States “failed miserably” in its goal, the island often falling quickly to China.13
It is important to note that since then, the idea of a quick and decisive war has been more regularly questioned. The difficulties of any Chinese amphibious invasion of Taiwan, for instance, have been seen in a set of war games run by CSIS.14 In a majority of the 24 run-throughs of the game, the Chinese amphibious assault failed—though it extracted heavy losses on U.S. and Taiwan forces.
If this is right—and history and technology points very much in the direction of this being right—then the failure of a Chinese amphibious invasion will almost certainly not end any war, but likely extend it to many months or even years. Moreover, Chinese military maneuvers staged around Taiwan in the last two years indicate that China may favor an interdiction strategy over an invasion. Instead of undertaking a very risky and uncertain invasion of Taiwan, China might instead use their geographic location to cut the island off from the outside world, forcing the United States to expose its valuable military assets to reestablish connections. Once again, that is a recipe for a longer war.
Here is where allies can make all the difference. Wars are rarely won by the military equipment on hand when it starts; more often they are won by equipment built during its course. For the United States, this poses a real alliance question. Though we cannot be certain, odds are that the United States would enter any war with China with a significant technological advantage. This could lead the United States to inflict considerably more damage to the Chinese military than vice versa in the opening stages.
However, once the war lengthens out of its opening the fighting will be determined by equipment built after its commencement. This would see the pendulum swing toward China. Chinese manufacturing capacity is considerably larger than the United States, and with a large amount of productive facilities at its beck and call, the Chinese military will start gaining a significant numerical—if not qualitative—advantage over its U.S. rival.
One example of this advantage would be UAVs/drones, which are dominating much of the battlespace in Ukraine and Russia. China has the existing capacity to produce many times more UAVs than the United States. Indeed, it has recently been estimated that one Chinese company, DJI Technology Company, controls 90 percent of the US commercial drone market share and 80 percent of the global market.15
To compete with such manufacturing capabilities, the United States would be desperate to tap the manufacturing prowess of Japan and South Korea, both of which have superior capabilities to the U.S. in some areas such as shipbuilding (as mentioned earlier). The question the United States would face is whether its allies would willingly turn themselves into a U.S. production asset—with China only hundreds of miles away.
What holds sway in production would be equally true for logistics. To fight a long war over Taiwan, the United States would be strengthened considerably by access to the bases, supplies, and repair facilities of allies such as Japan, the Philippines, Australia, and Singapore. Overall, these allies would provide wonderful facilities to bottle up Chinese shipping in waters close to the Chinese shore while allowing the United States real flexibility in deciding where and how to act.
In fact, a significant amount of study supports the idea that without South Korea and Japan by its side, the United States’ ability to fight for Taiwan might be severely—perhaps even fatally—compromised. South Korea could undertake a range of different operations, from threatening North Korea (potentially diverting Chinese forces) to intelligence gathering and even directly threatening Chinese naval and air forces in the Yellow Sea.16
Japan might be even more important to the determination of any war over Taiwan, for reasons of both capabilities and logistics. The country, with its growing air-sea denial forces, could play a key role in limiting the range of China’s operations—helping to hem in Chinese naval forces, for instance, to waters to the west of Japan (including the Ryukyu Islands).17
Logistically, Japan provides a depth and range of facilities for the United States, the denial of which would be very difficult to compensate for.18 Without Japanese bases, the United States would have to rely more and more on its Marianas bases (Guam), which are more than a thousand miles farther from the Chinese coast.
Yet, for well-known political reasons, the United States at present cannot count on South Korea or Japan providing even logistical aid—let alone militarily confronting China.19 If, in the end, the South Koreans and Japanese stand fully aside, the United States will struggle to support Taiwan to such a degree that it might not even be worth attempting to defend the island. In this way, U.S. allies could very well determine not only the outcome of any war with China, long or short, but if such a war can even be fought effectively in the first place.
One of the strangest developments of the last years is that both China and the United States (at least under the Trump administration) seem to be going out of their way to antagonize countries that would like to be their friends, or at least more friendly toward them. China’s aggressiveness has angered almost every country off its coast, from Japan (where the Chinese claim the Senkaku Islands) to Taiwan (which the Chinese claim) to the aforementioned South China Sea, which has brought into the conflict the Philippines, Malaysia, and Vietnam. Beijing has also seen greater tensions in their relations with Seoul, as they seem increasingly angry at the defense relationship between South Korea and the United States.20 Instead of picking and choosing to try and break apart a possible U.S.-led alliance, China seem to be going out of its way to scare possible U.S. allies.
If only the United States could take advantage of this dynamic—but so far, it has failed, and it looks like things will get worse. The rise of political populism in the United States, exemplified by the second election of Trump, has seen much of U.S. foreign policy recast as a zero-sum, often directly bilateral game. In this era, U.S. allies are seen as perfidious scroungers, trying to make the United States defend them while stealing U.S. jobs to boot. Trump himself made this very clear in an interview in July 2024. He claimed that Taiwan should be paying the United States for its defense, saying that the United States was “no different than an insurance company,” while Taiwan “doesn’t give us anything.”21 He went on to say that Taiwan was stealing the U.S. semiconductor industry.
This kind of language is no different than that used about U.S. allies in Europe—and does seem to herald a growth of isolationism and detachment within a significant part of the U.S. electorate. If this happens, the idea that the United States would actually be able to knit together a stronger alliance—which it very much needs—is questionable.
It is hardly comforting to realize that neither China nor the United States understand the value of allies. Instead of being drags, allies are almost always vital to winning wars and establishing predominance in times of peace. Those who try to frame the Indo-Pacific as a U.S.-China area of confrontation would do well to remember this. It could very well be that the power that does understand this is the power that prevails in the struggle for control of the Indo-Pacifc—the most vital area of the world, economically and strategically.
Phillips P. O’Brien is the chair of strategic studies and head of the School of International Relations at the University of St Andrews.
This brief is made possible by general support to CSIS and the support of the America in the World Consortium.
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