There are many reasons to fear an impending Chinese attack on Taiwan: Intensified Chinese aerial activity. High-profile Pentagon warnings. Rapid Chinese military modernization. President Xi Jinping’s escalating rhetoric. But despite what recent feverish discussion in foreign policy and military circles is suggesting, the U.S. withdrawal from Afghanistan isn’t one of them.

Some critics of President Biden’s decision to withdraw from Afghanistan argue the move will embolden Beijing because it telegraphs weakness — an unwillingness to stick it out and win wars that China will factor in when deciding whether to attack Taiwan, which it considers to be part of its territory.

The reality is, though, that the U.S. departure from Afghanistan will more likely give pause to Chinese war planners — not push them to use force against Taiwan.

The Chinese Communist Party’s stated goal is “national rejuvenation”: Regaining China’s standing as a great power. Chinese leaders and thinkers have studied the rise and fall of great powers past. They have long understood that containment by the United States could keep China from becoming a great power itself.

Luckily for Beijing, the Afghan war — along with Iraq and other American misadventures in the Middle East — distracted Washington for two decades. While China was building roads and ports from Beijing to Trieste, Italy, fueling its economy and expanding its geopolitical influence, the United States was pouring money into its war on terrorism. While Beijing was building thousands of acres of military bases in the South China Sea and enhancing its precision-strike capabilities, the U.S. military was fighting an insurgency and dismantling improvised explosive devices.

In many ways, it was just dumb luck that Mr. Xi and his predecessors, thanks in part to the war in Afghanistan, could build national power, undermine international norms, co-opt international organizations and extend their territorial control all without the United States thwarting their plans in any meaningful way.

But the end of the war in Afghanistan could bring these good times — which the Communist Party calls the “period of important strategic opportunities” — to an abrupt end. Sure, over the past 10 years American presidents tried to get back into the Asia game even as the war continued. Barack Obama asserted we would pivot to Asia back in 2011. Donald Trump’s national security team made great power competition with China its top priority.

But neither went much beyond paying lip service. The withdrawal shows Mr. Biden is truly refocusing his national security priorities — he even listed the need to “focus on shoring up America’s core strengths to meet the strategic competition with China” as one of the reasons for the drawdown.

Such a refocusing comes not a moment too soon. Chinese expansion and militarization in the South China Sea, deadly skirmishes with India, its crackdown in Hong Kong and repression in Xinjiang all point to an increasingly confident and aggressive China. In particular, Chinese military activity around Taiwan has spiked — 2020 witnessed a record number of incursions into Taiwan’s airspace. The sophistication and scale of military exercises has increased as well. These escalations come alongside recent warnings from Mr. Xi that any foreign forces daring to bully China “will have their heads bashed bloody” and efforts toward “Taiwan independence” will be met with “resolute action.”

The U.S. policy toward Taiwan is “strategic ambiguity” — there is no explicit promise to defend it from Chinese attack. In this tense environment, U.S. policymakers and experts are feverishly considering ways to make U.S. commitment to Taiwan more credible and enhance overall military deterrence against China. A recent $750 million arms sale proposal to Taiwan is part of these efforts, as is talk of inviting Taiwan to a democracy summit, which undoubtedly would provoke Beijing’s ire.

Some have argued that America’s withdrawal from Afghanistan undermines efforts to signal U.S. support for Taiwan. On the surface, it may seem as if the U.S. withdrawal would be a good thing for China’s prospects at what it calls “armed reunification.” Indeed, this is the message the nationalist Chinese newspaper The Global Times is peddling: The United States will cast Taiwan aside just as it has done with Vietnam, and now Afghanistan.

However, the American departure from Afghanistan creates security concerns in China’s own backyard that could distract it from its competition with the United States. Beijing’s strategy to protect its global interests is a combination of relying on host nation security forces and private security contractors and free-riding off other countries’ military presence. Analysts have concluded that China is less likely than the United States to rely on its military to protect its interests abroad. Beijing appears committed to avoiding making the same mistakes as Washington — namely, an overreliance on military intervention overseas to advance foreign policy objectives.

Now there will be no reliable security presence in Afghanistan and undoubtedly broader instability in a region with significant economic and commercial interests for China. Chinese leaders are also worried that conflict in Afghanistan could spill across the border into neighboring Xinjiang, where Beijing’s repressive tactics have already been the cause of much international opprobrium.

The reality is, the United States stayed much longer in Afghanistan than most expected. This upsets China’s calculus about what the United States would do in a Taiwan crisis, since conventional wisdom in Beijing had been that the painful legacy of Somalia would deter Washington from ever coming to Taipei’s aid.

But U.S. interventions in Afghanistan and Iraq have called these assumptions into question. Taiwan, with its proportionately large economy and semiconductor industry, is strategically important to the United States. U.S. power and influence in East Asia are reliant on its allies and military bases in the region and America’s broader role as the security partner of choice. If Taiwan were to fall to Chinese aggression, many countries, U.S. allies included, would see it as a sign of the arrival of a Chinese world order. By comparison, Afghanistan is less strategically important, and yet the United States stayed there for 20 years.

This does not bode well for any designs Beijing might have for Taiwan.

It’s true that China would benefit from a home-field advantage given Taiwan’s proximity, and that Beijing’s arsenal is far greater than Taiwan’s. China, too, would likely enjoy more domestic public support for any conflict than the U.S. would for yet another intervention.

But if China has any hope of winning a war across the Strait, its military would have to move fast, before the United States has time to respond. Chinese planners know that the longer the war, the greater the U.S. advantage. Unlike Chinese production and manufacturing centers, which can all be targeted by the United States, the American homeland is relatively safe from Chinese conventional attack. China is far more reliant on outside sources for oil and natural gas, and thus vulnerable to U.S. attempts to cut off its supply.

And the Chinese economy would suffer more: Since the war would be happening in Asia, trade would be bound to be disrupted there. The United States would need to stick it out for only a short time — not 20 years — for these factors to come into play.

A call on Thursday between Mr. Biden and Mr. Xi hinted at the stakes — the two “discussed the responsibility of both countries to ensure competition does not veer into conflict,” according to the White House.

Chinese leaders already expected a tense relationship with the Biden administration. Now they are faced with the fact that the United States might have the will and resources to push back against Chinese aggression, even if it means war.

So, while there may be other reasons to oppose the end of the war in Afghanistan, the impact on China’s Taiwan calculus is not — and should not be — one of them.