How Might a US-China War Really Start?

If it happens, it will be the most apocalyptic war in generations. A conflict so brutal, so devastating it could eclipse even Russia’s invasion of Ukraine. In the last few years, the idea of a US-China war has gone from a fringe possibility to something both sides openly speculate about.

The reasons for this are myriad, ranging from generic great power competition to incredibly specific issues like China’s stance towards Taiwan. A terrifying number of people now agree such a conflict is possible. Yet for all these Cassandras may be proven right, there is one thing no one can say for sure—one thing that will remain a mystery until the moment it happens: how a US-China war actually starts.

On the face of it, the answer seems simple. A full-blown invasion of Taiwan is the nightmare that keeps Pentagon planners up at night. But that is not the only scenario in play.

From a collision in the South China Sea to a grave miscalculation over the Philippines, there are numerous potential trigger points that could soon unleash the biggest war in decades.

The Thucydides Trap and 600 Years of Great Power Conflict

In 2017, a new book made waves in American national security circles. Written by political scientist Graham T. Allison and titled Destined for War, it sought to place the growing US-China rivalry into deep historical context—to understand how likely it was that conflict would break out between the world’s two great powers.

The unfortunate answer: it could be very likely. Allison’s approach was to step back from debates over Taiwan or trade wars and instead focus on a phenomenon he found across history: the Thucydides Trap. Thucydides, an Athenian general, wrote a history of the devastating Peloponnesian War between Athens and Sparta.

When casting around for a trigger for this carnage, he hit upon a brilliantly simple explanation: “It was the rise of Athens and the fear that this instilled in Sparta that made war inevitable.” It was this sentence that Allison used to popularize the Thucydides Trap concept—the fear that overtakes an established great power when a new challenger begins to rise, a fear that can ultimately make war all but inevitable. Along with the Harvard Belfer Center, Allison applied this concept to the last 600 or so years of history.

In that span of time, he identified 16 separate moments when a rising power threatened to overtake an established one. In all but four cases, they wound up going to war. Recent examples include the rise of Prussia in the mid-19th century that led to the Franco-Prussian War, or the rise of Japan in the late 19th century that led to conflicts with both China and Russia.

Staying with Japan, it was the empire’s continued expansion into the Pacific that led to the United States entering WWII. Meanwhile, a rising Germany led to not one but two wars with the European powers of France and Britain. From the Hapsburg-Valois Wars of the 16th century to the two World Wars, the arrival of a new power tends to trigger violence.

Today, that new power—the rising Athens—is China. And the USA is old, worried Sparta. This is why so many believe a Sino-American war is on the horizon, and why someone like James Crabtree, Asia director for the International Institute of Strategic Studies, can warn: “On our current course some kind of military confrontation between the US and China over the coming decade now looks more likely than not.”

When the Trap Failed to Spring—and When It Did

Such a conflict is not a done deal. While the Harvard Belfer Center only documents four instances when the Thucydides Trap failed to spring, three of them were in the modern era. First, when America displaced the British Empire as the great global power.

Second, when the USSR challenged American supremacy. And third, when a reunified Germany became Europe’s new powerhouse in the 1990s. In each case, the established great powers found a way to accommodate the newcomer.

The British Empire backed off from the Western hemisphere. The USA and USSR managed to find other outlets—like the Space Race—to express their rivalry. Reunified Germany eschewed military might.

It is not impossible to imagine a future in which the China-US rivalry gets added to this small list, a future in which trade wars and cutthroat competition never cross the line into real war. On the other hand, it is even easier to imagine a future in which everything goes catastrophically wrong. Dig into the 12 examples when great power rivalry turned into full-blown conflict, and there is—as the National Interest put it—an overabundance of cases where “the proximate causes of war included accidents, unforced errors, and unintended consequences of unavoidable choices in which one of the protagonists accepted increased risks hoping that another would back down.”

In other words, wars erupted not because one side deliberately sought conflict, but because random events led them down an escalatory path with one inevitable outcome. Famously, this includes World War One, where the chance assassination of the Austro-Hungarian heir by a 19-year-old in Bosnia plunged Europe’s powers into an entirely avoidable meatgrinder. But it also includes the Franco-Prussian War, which was sparked—of all things—by a telegram describing a rude diplomatic encounter in Ems.

Or the Russo-Japanese War, which only ignited after the Russians blithely crossed one too many Japanese red lines, without ever really believing Tokyo was serious about enforcing them. While it is entirely possible a Sino-American war will be sparked by a Chinese armada bearing down on Taiwan, it is also possible the trigger will not be anything so clear cut—that both sides will simply miscalculate over a flashpoint and accidentally set the doomsday machine in motion.

Gray Zone Flashpoint: The Taiwan Strait

For those who believe Beijing is gunning for military confrontation with America, the 2020s represent a worrying time. The tail end of this decade will see the US retire a large chunk of its naval force, including submarines, ships, and planes. While this will give way to a much-improved Asia-Pacific presence in the 2030s, it means there is a narrow window of time in which China will potentially have the upper hand.

Add to that Xi Jinping’s widely reported order for his military to be ready to invade Taiwan by 2027, and the next few years might give Pentagon planners the sweats. The fear is that Beijing will decide it has a critical window of time to attack the island democracy while America is weaker than normal. That ticking clock could lead Xi Jinping to gamble on a dangerous course of action, one which might involve a devastating surprise attack on US forces in the Pacific to keep them from coming to Taiwan’s aid—a modern-day Pearl Harbor.

Yet there are reasons to think this is not the most likely way things could blow up around Taiwan. For one thing, there is the cost calculation for China in launching a full assault on the island, one that could wind up gaining Xi Jinping little more than smoldering ruins. China would prefer unification with Taiwan, which it views as a breakaway province, to be as bloodless as possible.

A war could devastate the Taiwanese economy, especially in the vital semiconductor industry. Even an America bloodied by a surprise attack would still be a formidable foe, one that Xi Jinping knows would never let the deaths of American servicemen in Pacific bases go unpunished. All of which may be why the experts quoted in Air and Space Forces did not rank a full-blown invasion as the likeliest spark around Taiwan.

Instead, that designation went to an accident or miscalculation in the Taiwan Strait. China’s official position on Taiwan is that it is a renegade province still officially, legally part of China. Beijing therefore believes the 12 nautical miles around Taiwan are its sovereign territory and, under Chinese law, there are no competing claims on the waters of the Taiwan Strait.

The Strait, stretching for 160 km between the mainland and Taiwan, is one of the most important shipping channels on Earth. Because Beijing considers Taiwan its territory, it recognizes no claims other than its own. China guards its maritime Exclusive Economic Zones jealously.

According to the United Nations Convention on the Law of the Sea, vessels in EEZs have “freedoms of navigation and overflight and other internationally lawful uses of the sea.” But China denies this, which is why the US and its allies routinely sail warships through the Strait to make a point about freedom of navigation. This means American and Chinese vessels often get into close calls.

In June 2023, a Chinese warship nearly crashed into an American boat. Above the Strait exists an invisible barrier known as the Davis Line—the midway point between China and Taiwan, marking where the two nations’ air defense identification zones meet. Between 1954 and 2020, Chinese aircraft crossed to the Taiwanese side only four times.

Since then, Beijing has crossed the Davis Line hundreds of times. In one month in 2022 alone, Taiwan logged nearly 450 violations. Each time this happens, it raises the possibility of an incident—one that would initially blow up between China and Taiwan but could quickly drag in the US, Japan, the Philippines, Australia, and perhaps the world.

The South China Sea and the Philippines Flashpoint

In his magisterial book on the causes of the First World War, The Sleepwalkers, Christopher Clarke spends time dwelling not just on how unlikely war seemed, but how unthinkable its eventual shape was. The British spent the early 1900s worrying that the next great war would be sparked not in the Balkans but in their Indian colonies, and they thought they would be fighting an imperialist Russia, not Germany. History rarely unfolds as expected.

While the greatest tensions between the US and China are around Taiwan, the island democracy and its waters are not the only potential flashpoints. If Beijing’s claims over the Taiwan Strait are legally dubious but at least have an internal logic, then its claims on the South China Sea are simply dubious. For years, Beijing has been claiming sovereignty over nearly the entire sea—a place of such value to global trade that it makes even the Taiwan Strait look middling.

This is a claim no one else agrees with. As the BBC has noted, an international court ruled in 2016 that “the assertion has no legal basis.” But that has not stopped Beijing from trying to boost its claim by reclamation projects, constructing artificial islands, or by swiping other nations’ territory.

One nation that has suffered this in recent years is the Philippines. In 2012, China seized control of Scarborough Shoal, an uninhabited atoll claimed by Manila. Since then, Beijing has aggressively muscled in on the country’s remoter reaches.

Filipino fishermen are frequently driven away from their traditional grounds near the Spratly Islands. Manila was forced to file more than 200 diplomatic complaints against Chinese vessels. In February, a Chinese patrol shone a military-grade laser at a Filipino coast guard boat to stop it from reaching an atoll.

The connection to the US is direct. In 2019, a Chinese plan to build a $2 billion smart city on the Philippine island of Fuga caused a scandal in Manila’s security establishment. Although then-president Rodrigo Duterte tried to keep relations friendly with Beijing, the incident convinced the Trump administration to send a signal.

Accordingly, Secretary of State Mike Pompeo reaffirmed the 1951 Mutual Defense Treaty—a treaty that commits the US to come to Manila’s aid if any of its armed forces, planes, or coastal patrol vessels is attacked. Since Bongbong Marcos took power in 2022, the Philippines has taken an increasingly hawkish approach to China, ordering more naval patrols and increasing defense cooperation with the US, Australia, and Japan, including giving American aircraft access to four strategically important Philippine bases. Washington has once again reaffirmed the Mutual Defense Treaty and is now talking about running joint Philippine-US patrols of contested waters, possibly joined by Australia.

As the Quincy Institute for Responsible Statecraft wrote: “A Philippines-China clash, with the United States and perhaps Australia frontally present in the theater as an ally, can plausibly escalate to a great power conflict.”

Beijing’s Encirclement Fears and the Risk of ‘Teachable Moments’

An American presence might not stop Beijing from menacing Manila’s ships—the opposite may be the case. If China believes the Philippines to be part of an American strategy of encirclement, it might increase the sense that Beijing is under siege and needs to lash out to protect its interests. The Atlantic recently described Beijing’s habit of using “teachable moments”—short, sharp bursts of violence—to make its enemies back off.

One such moment might come in the form of a surprise attack on Filipino bases on hard-to-defend islands that the PLA could quickly overrun. In that scenario, the US would have to either meekly turn a blind eye or risk a Pacific conflagration over a handful of small, sparsely populated islands claimed by an ally. Manila is not America’s only regional ally trying to stop China encroaching on its turf.

There is also Japan. The US-Japan security treaty contains Article Five, which states that an attack on one of the allies is an attack on all. This compels Washington to come to Tokyo’s aid if it is attacked.

Recent Chinese aggression towards Japan is relevant because if that aggression ever turns to violence, Article Five could force America into fighting its first Pacific war in decades—a war perhaps sparked by a clump of uninhabited rocks nearly 2,000 km from Tokyo. Known as the Senkaku Islands in Japan, these tiny rocks near Taiwan are Tokyo’s version of Manila’s island problem. Claimed by Beijing under the name Diaoyu Islands, these outcrops have been the scene of intense Chinese naval activity in recent years.

The year 2022 saw China’s ships spending a record amount of time loitering nearby. This has caused anxiety in Japan’s security establishment for two good reasons: the Senkakus help protect Tokyo’s vital trade routes, and Beijing might well use violence to secure them. In 2021, Beijing updated its laws to allow the Chinese Coast Guard to use force to protect national sovereignty.

Since China already defines the Senkakus as part of its territory, Beijing would feel justified using weapons to drive Japan away.

Japan’s Military Buildup and the Expanding Web of Alliances

It is thanks to threats like these that Tokyo now regards China as an immediate, existential threat—one almost as dangerous to Japan as Russia is to Ukraine. That is not a blithe comparison. As Foreign Policy detailed, the Russian attack on Ukraine seriously spooked the Japanese: “That a major power armed with nuclear weapons could invade a neighbor with impunity, seeking to unilaterally change borders by force, shook Japan to the core.”

The nuclear factor is key. Tokyo watched, horrified, as the world hesitated about supporting Ukraine over fear of nuclear escalation. Tokyo watched Vladimir Putin’s bellicose threats to use Russia’s arsenal against its smaller neighbor.

The parallels of nuclear-armed China encroaching on non-nuclear Japan’s territory were painfully clear. Prime Minister Fumio Kishida declared: “Ukraine is the future of Asia.” More telling still was the national security strategy document released in December 2022, which labeled China “the greatest strategic challenge ever to securing the peace and stability of Japan.”

Tokyo is now desperately scrambling to respond. Under new guidelines, Japan is moving to boost its defense spending to 2 percent of GDP by 2027—a change that would make it the third-largest military spender in the world. Japan will also engage in the largest buildup of its armed forces since WWII, using this money to turn many of its remote islands into hardened bases studded with anti-ship missiles and air defenses.

Some of those bases will also be armed with American Tomahawk cruise missiles capable of hitting mainland China. The new guidance also reinterprets the constitution’s self-defense clause to allow for a devastating preemptive strike if an attack is believed imminent. Not all of this is driven by fears over China—North Korea is a real and present threat to Japan and has fired missiles over the country in recent years—but the biggest audience is clearly Beijing.

Tokyo has also been building a growing system of alliances. As well as its security treaty with Washington, Japan has put new emphasis on its relationship with fellow Quad members India and Australia. There has been increased outreach to the Philippines and even Japan’s historic enemy, South Korea.

Prime Minister Kishida traveled to Kyiv to meet Zelensky and became one of the few Asian leaders to wholeheartedly join sanctions on Russia. Great as all this is for Tokyo’s defense, it comes with a serious downside: this web of alliances increases the chance of a local conflict expanding into a globe-spanning war. The Atlantic noted how Beijing has been looking to pick a fight with Tokyo for decades: “For years, Chinese strategists have speculated about a short, sharp war that would humiliate Japan, rupture its alliance with Washington, and serve as an object lesson for other countries in the region.”

That might come in the form of an invasion of the Senkakus, or maybe in the form of lightning strikes on the new bases—especially if China believes there is a chance Japan might use them to attack first.

The Invidious Choice and the Specter of Inevitability

A flare-up with Japan would again put the US in an invidious position—one in which Washington either refuses to come to Japan’s aid and looks weak and unable to protect its allies, or risks tens of thousands of Americans dying to help Tokyo retaliate. It would be a horrific choice. While a full-scale invasion of Taiwan would probably see the American public rally behind military action—doubly so if it opened with Chinese attacks on US Pacific bases—would they be willing to risk uncountable numbers killed to retake the Senkakus?

On the other hand, could the US stomach looking weak and unreliable before its enemies? There are no easy answers. These are just some of the myriad ways that the doomsday machine might be set in motion, that the Thucydides Trap might spring shut and plunge Asia Pacific into renewed great power conflict.

Whether it is a trap that can be avoided remains uncertain. The signs are not encouraging. Washington and Beijing are barely talking.

In the military establishments of both nations, a fatalism seems to be creeping in—a feeling that war is inevitable, no matter how dreadful it might be. Perhaps the only question left is how it will start. The possibilities range from a full-scale invasion of Taiwan to an accidental collision in the Taiwan Strait, from a miscalculation over Philippine islands to a short, sharp strike on the Senkakus.

But the truth is that no one knows for sure, any more than Europeans at the start of 1914 knew their world would be undone by a gunshot in Sarajevo. All anyone can try to do is be aware of the dangers and tread carefully—because the last thing the world needs, decades from now, is for some historian to sum up this era with the simple words: “It was the rise of China, and the fear that this instilled in America, that made war inevitable.”

Sources

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