This essay was originally published in Foreign Affairs magazine.

But the United States and its allies could do more to punish Russia. They could bar all transactions with Russia, whether trade or financial. They could seize all Russian assets within their jurisdictions. Washington could announce secondary sanctions on anyone using U.S. dollars for any transaction with Russia. Most important, the United States could use these and other measures to prevent Russia from exporting oil and gas. Letting Russia continue to export oil and gas would be like letting China sell consumer electronics even after it had taken Taiwan by force.

If the United States and its allies have been cautious in their response to Russia, they are likely to be even more restrained when responding to China — and Beijing knows it. China’s ability to retaliate against the West with economic sanctions of its own is much greater than Russia’s. Singapore, which announced trade and banking restrictions against Moscow, trades about $2.5 billion worth of goods with Russia each year — but $57 billion worth of goods with China. China’s leaders likely do not fear U.S.-led economic sanctions in the event of a Taiwan takeover because they probably think that China’s own productive capacity, resources, and friendly partners will allow them to survive on their own, especially since China will soon be the world’s largest economy. They are probably right. China could absorb the types of sanctions being imposed on Russia. And given China’s ability to inflict pain on Western countries, any measures levied against Beijing would likely be softer than those imposed on Moscow.

Taiwan Is Not Ukraine

The Western military response to Russia’s invasion of Ukraine will have an even smaller impact than sanctions on China’s thinking about Taiwan. True, neither the United States nor NATO has deployed troops to fight on Ukraine’s behalf. And U.S. military assistance to Ukraine has been modest: late last month, President Joe Biden instructed the State Department to release up to an additional $350 million worth of weapons from U.S. stocks to Ukraine.

But Russia would have to invade a NATO ally without provoking a U.S. military response for Chinese leaders to seriously question Washington’s commitment to defending Taiwan. Biden has made clear from the beginning of the crisis that his administration will never send troops to Ukraine—a stark contrast with his rhetoric on Taiwan. Just last week, Biden stated unequivocally that the United States would defend Taiwan in the event of a Chinese attack. As a show of support, he also sent to the island a delegation of former U.S. officials led by Mike Mullen, a former chairman of the Joint Chiefs of Staff.

In any case, Chinese planners largely assume the United States would intervene militarily on behalf of Taiwan. What some of them question is whether the United States could amass enough forces fast enough to blunt a Chinese assault on the island. Ironically, if the United States had launched a military operation in response to Russia’s invasion of Ukraine, Chinese leaders would have had further reason to question Washington’s ability to thwart a Chinese assault on Taiwan. The United States does not have the resources to fight the Russians in Europe and prepare adequately for a great-power war in Asia.  

Of course, these facts have not prevented China from trying to manipulate the narrative to undermine Taiwan’s resolve. Chinese state media has been flush with stories about how the United States did not come to Ukraine’s aid and therefore won’t come to Taiwan’s either. Like much of what appears on Chinese state media, however, these stories reflect what Chinese leaders want the world to believe—not what they believe themselves.

Not the Right Time

Chinese leaders are without a doubt considering an attack on Taiwan, but now is not the right time. China’s military is still honing the capabilities it would need to take and hold the island. And Xi is unlikely to take a dangerous gamble on Taiwan before the next Party Congress in late 2022, when he is widely expected to secure a third term as general secretary of the Chinese Communist Party. Xi is also working hard to lessen China’s technological dependence on the West, thus minimizing the impact on any further decoupling after a possible war. For all these reasons, an assault on Taiwan before 2025 is unlikely.

If anything, the crisis in Ukraine creates an additional incentive for China to wait. Beijing does not want the world to equate the two scenarios. From China’s perspective, Ukraine is an independent country engaged in a border dispute with Russia. Taiwan, by contrast, “has always been an inalienable part of China’s territory,” as China’s ambassador to the Association of Southeast Asian Nations, Deng Xijun, put it late last month. In other words, linking the two issues would undermine China’s claim to the island.

China also understands that moving against Taiwan now would solidify fears in the West of an axis of autocrats. The United States may not have the resolve to fight a protracted war to defend Taiwan. But suddenly faced with a need to defend freedom and democracy against an authoritarian alliance, Washington could muster a greater military response and convince its allies to do the same. Partly for this reason, China has desperately tried to maintain some semblance of neutrality during the Ukrainian crisis.

Russia’s invasion of Ukraine has certainly changed aspects of the international order. It has rallied European countries against Russia, prompted Germany to increase defense spending, and even convinced historically neutral countries such as Finland, Sweden, and Switzerland to take a stance against Moscow. From China’s perspective, however, nothing Russia or its adversaries have done meaningfully alters the calculus on Taiwan. 

This commentary was originally published by The Wall Street Journal.

A Russian invasion of Ukraine would be the most consequential use of military force in Europe since World War II and could put Moscow in a position to threaten U.S. allies in Europe. Many in the American foreign-policy establishment argue that the appropriate U.S. response to any such invasion is a major American troop deployment to the Continent. This would be a grave mistake.

The U.S. can no longer afford to spread its military across the world. The reason is simple: an increasingly aggressive China, the most powerful state to rise in the international system since the U.S. itself. By some measures, China’s economy is now the world’s largest. And it has built a military to match its economic heft. Twenty-five years ago, the Chinese military was backward and obsolete. But extraordinary increases in Beijing’s defense budget over more than two decades, and top political leaders’ razor-sharp focus, have transformed the People’s Liberation Army into one of the strongest militaries the world has ever seen.

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China’s new military is capable not only of territorial defense but of projecting power. Besides boasting the largest navy in the world by ship count, China enjoys some capabilities, like certain types of hypersonic weapons, that even the U.S. hasn’t developed.

Most urgently, China poses an increasingly imminent threat to Taiwan. Xi Jinping has made clear that his platform of “national rejuvenation” can’t be successful until Taiwan unifies with the mainland—whether it wants to or not. The PLA is growing more confident in its ability to conquer Taiwan even if the U.S. intervenes. Given China’s military and economic strength, China’s leaders reasonably doubt that the U.S. or anyone else would mount a meaningful response to an invasion of Taiwan. To give a sense of his resolve, Mr. Xi warned that any “foreign forces” standing in China’s way would have “their heads . . . bashed bloody against a Great Wall of steel forged by over 1.4 billion Chinese people.”

The U.S. must defend Taiwan to retain its credibility as the leader of a coalition for a free and open Indo-Pacific. From a military perspective, Taiwan is a vital link in the first island chain of the Western Pacific. If Taiwan falls into Chinese hands, the U.S. will find it harder to defend critical allies like Japan and the Philippines, while China will be able to project its naval, air and other forces close to the U.S. and its territories. Taiwan is also an economic dynamo, the ninth-largest U.S. trading partner of goods with a near-monopoly on the most advanced semiconductor technology—to which the U.S. would most certainly lose access after a war.

The Biden administration this month ordered more than 6,000 additional U.S. troops deployed to Eastern Europe, with many more potentially on the way. These deployments would involve major additional uncounted commitments of air, space, naval and logistics forces needed to enable and protect them. These are precisely the kinds of forces needed to defend Taiwan. The critical assets—munitions, top-end aviation, submarines, and intelligence, surveillance and reconnaissance capabilities—that are needed to fight Russia or China are in short supply. For example, stealthy heavy bombers are the crown jewel of U.S. military power, but there are only 20 in the entire Air Force.

The U.S. has no hope of competing with China and ensuring Taiwan’s defense if it is distracted elsewhere. It is a delusion that the U.S. can, as Pentagon press secretary John Kirby said recently, “walk and chew gum at the same time” with respect to Russia and China. Sending more resources to Europe is the definition of getting distracted. Rather than increasing forces in Europe, the U.S. should be moving toward reductions.

There is a viable alternative for Europe’s defense: The Europeans themselves can step up and do more for themselves, especially with regard to conventional arms. This is well within Europe’s capacity, as the combined economic power of the NATO states dwarfs that of Russia. NATO allies spend far more on their militaries than Russia. To aid its European allies, the U.S. can provide various forms of support, including lethal weapons, while continuing to remain committed to NATO’s defense, albeit in a more constrained fashion, by providing high-end and fungible military capabilities. The U.S. can also continue to extend its nuclear deterrent to NATO.

The U.S. should remain committed to NATO’s defense but husband its critical resources for the primary fight in Asia, and Taiwan in particular. Denying China the ability to dominate Asia is more important than anything that happens in Europe. To be blunt: Taiwan is more important than Ukraine. America’s European allies are in a better position to take on Russia than America’s Asian allies are to deal with China. The Chinese can’t be allowed to think that America’s distraction in Ukraine provides them with a window of opportunity to invade Taiwan. The U.S. needs to act accordingly, crisis or not.

Ms. Mastro is a center fellow at the Shorenstein Asia-Pacific Research Center, part of Stanford’s Freeman Spogli Institute for International Studies, and a nonresident senior fellow at the American Enterprise Institute. Mr. Colby is a principal at the Marathon Initiative and author of “The Strategy of Denial: American Defense in an Age of Great Power Conflict.”