It doesn’t often happen that ordinary Chinese say publicly that they’re disappointed with their government. That they’re ashamed of their government. That they want to renounce their Communist Party memberships. And that they think the People’s Liberation Army is a waste of taxpayers’ money.

It’s even rarer that such angry comments come from the kind of nationalists who usually support whatever their leaders demand of them.

For much of Monday and Tuesday, many Chinese applauded the tough rhetoric from government, military and media personalities who were attempting to thwart Speaker Nancy Pelosi’s visit to Taiwan. Then, as Ms. Pelosi’s plane was touching down in Taiwan late Tuesday night, some social media users commented on how disappointed they were with Beijing’s lame response.

No military action in the Taiwan Strait, as they felt they had been led to expect. No shoot-down, no missile attack, no fighter jet flying next to Ms. Pelosi’s plane. Just some denunciations and announcements of military exercises.

Many people complained that they felt let down and lied to by the government. “Don’t put on a show of power if you don’t have the power,” wrote a Weibo user with the handle @shanshanmeiyoulaichi2hao shortly after the flight’s landing. “What a loss of face!”

The user went on to say that the government didn’t deserve the people who had waited for hours to witness how history could be made. “A great nation. How ironic!”

The strong online emotions showed the complexity of the public opinion that Beijing will have to manage if it decides to invade Taiwan. And they demonstrated how nationalism is a double-edged sword that can be easily turned against the government. Some antiwar comments that managed to evade the censors, if only for a moment, also opened a window onto the psychological impact of the Ukrainian war on the Chinese public.

Some users compared the People’s Liberation Army to the Chinese men’s soccer team, a laughingstock in the country because it has qualified for the World Cup only once. They sneered at the announcement that the P.L.A. would conduct military exercises near Taiwan. “Save some gas,” said one WeChat user. “It’s very expensive now,” responded another.

On WeChat, the comments section for a short video about a military exercise became a board for dissatisfied people to whine. Among thousands of comments, a few Communist Party members said they would like to quit out of shame. A military veteran said he would probably never mention his army experience again. “Too angry to fall asleep,” commented a user with the handle @xiongai.

The comments section was later closed.

Many users seemed especially disappointed with the foreign ministry. “When China said ‘strongly condemn’ and ‘solemnly declare’, it was only for the purpose of amusing ordinary folks like us,” wrote a Weibo user with the handle @shizhendemaolulu, referring to the language that foreign ministry spokespersons used about Ms. Pelosi’s visit.

“So tough when it comes to domestic governance and so cowardly in foreign affairs,” the user wrote. “Utterly disappointed!”

On Wednesday afternoon, a spokeswoman for the foreign ministry, Hua Chunying, responded to a question about the public’s disappointment by saying that she believed the Chinese people were rational patriots and that they had confidence in their country and their government.

The Chinese Communist Party has used nationalism as a governing tool since the Mao era. Xi Jinping, China’s current paramount leader, took it to a new level. “Nationalism is becoming a core pillar of both the party’s and Xi’s personal political legitimacy,” Kevin Rudd, the chief executive of the Asia Society and a former prime minister of Australia, wrote in his book “The Avoidable War: The Dangers of a Catastrophic Conflict Between the U.S. and Xi Jinping’s China.”

The unification of Taiwan, a self-ruling democracy that Beijing considers part of its territory, with the mainland is a centerpiece of Chinese nationalism.

But as Mr. Rudd and others argue, it has sometimes proven difficult to control the nationalist genie once it is released from the bottle. “This problem has become progressively larger under Xi Jinping, as nationalist appeals have moved from the margins to the center of the Chinese propaganda apparatus across the board,” he wrote.

The online backlash this week is an example.

Most Chinese didn’t pay very much attention to Ms. Pelosi’s pending Taiwan visit until Monday afternoon, when a flurry of official and semiofficial statements led many to believe that China could take tough, possibly military, actions to deter it.

Zhao Lijian, a foreign ministry spokesperson who may be China’s best-known “wolf warrior” diplomat, warned the United States on Monday that the P.L.A. would “never sit idly by. China will definitely take resolute and strong countermeasures to defend its own sovereignty and territorial integrity.” On the website of People’s Daily, the official newspaper of the Communist Party, a two-paragraph article about his comments was viewed 2.7 million times.

That evening, the P.L.A.’s Eastern Theater Command, which covers Taiwan, posted on Weibo that it was waiting for the order to fight and would “bury all invading enemies.” The post was liked more than a million times, and the embedded video, featuring footage of bombings and explosions, has had more than 47 million views.

And then there’s Hu Xijin, the retired editor in chief of Global Times, the Communist Party tabloid that has played probably the biggest role in stoking Chinese nationalism over the past three decades.

Mr. Hu first suggested on Twitter last week that China should shoot down Ms. Pelosi’s plane if she visited Taiwan. On Weibo, he called on his nearly 25 million followers to “support all the countermeasures by the government and share the hatred of the enemy.”

“We will definitely launch strong countermeasures to hit the U.S. and Taiwan,” he wrote on Tuesday. “So hard that the Taiwan authorities will regret it.”

After Ms. Pelosi’s plane landed in Taipei, China issued many strongly worded condemnations and announced an intimidating array of military exercises around Taiwan. But the lack of any direct military action left many nationalists feeling shortchanged. Their heroes, including Mr. Hu and Mr. Zhao, lost some of their halos.

Now they have mocked Mr. Zhao by posting a short video of him making tough statements on Monday.

Late Tuesday night, Mr. Hu’s Weibo account was flooded with angry, sarcastic and abusive comments. “If I were you, I would be so embarrassed that I would not dare to say another word and hide until the day of Taiwan’s reunification,” commented a Weibo user with the handle @KAGI_02.

Ren Yi, a Harvard-educated nationalistic blogger, wrote a searing commentary early Wednesday morning, urging that Mr. Hu’s influence be reined in.

In a Weibo post, Mr. Ren said the public’s unmet high expectations could hurt the government’s credibility. He blamed those unrealistic expectations on Mr. Hu, saying that his posts had been taken too seriously because he once ran a party newspaper.

Mr. Ren isn’t the only person who wants to dethrone Mr. Hu, who is now a Global Times columnist, from his position as the most influential Chinese journalist. Other commentators and social media personalities are also asking that he be held accountable. Mr. Hu wrote on Weibo on Wednesday morning that he’d become a “punching bag.”

But some comments also pointed out that Mr. Hu was just one part of China’s response to Ms. Pelosi’s visit, and suggested that all the blame being pointed toward him could signal that the government might be looking for a scapegoat.

There are antiwar voices on Chinese social media, too. Some people argued that only online warmongers should be sent to the front lines. Some parents are worried that their children could be conscripted. Others tried to urge their compatriots to look at Ukraine and Russia to understand that war means death and economic destruction.

Zou Sicong, a writer who’s been traveling in Poland for the past few months, urged people on WeChat to have a realistic understanding of war, saying that he had learned about what Ukrainians and ordinary Russians had experienced.

People should be glad that nothing happened on Tuesday night, he said. “You should feel lucky that you can still do your business, pay your mortgage, go to work tomorrow, get tested for Covid and live,” he wrote. “Please pray for yourself and your loved ones that we can get out of this approaching storm intact.”