Just after US House Speaker Nancy Pelosi landed in Taiwan, she published an article arguing that her controversial visit was critical to demonstrating American support for the country as it faces mounting pressure from China.

“In the face of the Chinese Communist party’s accelerating aggression, our congressional delegation’s visit should be seen as an unequivocal statement that America stands with Taiwan,” Pelosi wrote in The Washington Post, as she became the highest-ranking American official to visit since then-Republican Speaker Newt Gingrich in 1997.

The California Democrat drew harsh rebukes from China, which threatened large-scale military exercises around Taiwan from Thursday. But she had also ignored pleas from the White House, which was worried about sparking a crisis.

President Joe Biden did not speak to Pelosi about the trip but he sent senior officials to explain the risks. Asked on Tuesday if Biden supported her trip, National Security Council spokesman John Kirby said that he “respects” her decision.

For Pelosi, the visit is the latest salvo in a career of standing up to China over issues that encompass its human rights record in Tibet and Xinjiang, its crackdown on democracy in Hong Kong and its aggressive military activity.

Carolyn Bartholomew, Pelosi’s former chief of staff, said the Speaker was acting out of a longstanding conviction that was partly sparked by the Tiananmen Square massacre in 1989.

“She was horrified, it was distressing to watch what was happening in Tiananmen Square. It was a defining moment in her view of China,” said Bartholomew, now a commissioner at the US-China Economic and Security Review Commission.

Bartholomew said Pelosi would have taken the risks outlined by the Biden team into account, but said she had to weigh many factors, including after the news of her plan leaked last month in the Financial Times.

“She is a woman who absorbs a lot of information. I am sure she gave serious thought to what they were telling her,” Bartholomew added. “Other reasons prevailed, and once the news broke, not going would have been a capitulation to China.”

Ryan Hass, a former White House National Security Council director for China and Taiwan, said Pelosi felt very strongly about supporting democratic partners that were under duress from authoritarian regimes.

“She has a long record of not bowing to Chinese pressure and feels passionately about upholding the principle of Congress being a co-equal branch of government,” Hass said.

The loudest praise in Washington for Pelosi came from an unusual quarter: Republicans who believed that abandoning her trip would have shown weakness. In the Senate, 26 of the 50 Republicans signed a statement supporting the visit.

Democrats were more notable in their silence. Pelosi came under criticism from some China experts, including former Australian prime minister Kevin Rudd, who told the BBC she was putting “fuel on the fire”.

“Taiwan is getting a bad deal, a permanent erosion of the security situation for a two-day sugar high,” said one China expert.

Craig Singleton, a China expert at the FDD think-tank, said Pelosi’s trip was a mistake that risked a major escalation in US-China tensions.

“The rhetoric from Beijing suggests this is not going to be a one-week affair. The drills they announced are very serious,” said Singleton who worried that the US would face the biggest Taiwan crisis in decades. “China is going to wield elements of power in coming days long after Pelosi returns to her very comfortable house in San Francisco.”

But others said the fact that China had not taken severe action as Pelosi arrived in Taiwan reinforced why the US should be less worried about ramifications. “Newt Gingrich proved that despite CCP sabre-rattling, the Speaker . . . can visit Taiwan if he wants to. Decades later, Nancy Pelosi proved that is still true,” said Rebeccah Heinrichs of the Hudson Institute think-tank.

While China rebuked Gingrich in 1997, its response to Pelosi has been harsher, partly because of the tense state of US-China relations and partly because the PLA is far stronger now than it was a quarter of a century ago.

Jennifer Rudolph, a China expert at Worcester Polytechnic Institute, said the global landscape had changed with China rising as a power.

“When Gingrich went to Taiwan, China was angry too,” said Rudolph. But she added: “We weren’t at the point where we are now with China actively challenging the US role in the world on multiple fronts [and] engagement is seen as dead in the water . . . That is what makes this moment so fraught.”

China also has a particular grievance with Pelosi stretching back to 1991, when during a visit to Beijing she visited Tiananmen Square and unfurled a banner that read: “To those who died for democracy in China.”

Richard Bush, a Taiwan expert at the Brookings Institution whose former boss went with Pelosi on the 1991 trip, said China was focused more on her character than the fact that the Speaker was constitutionally second in line to the presidency, after the vice-president.

“What is most important is whether they trust the intentions of the person they are dealing with, and with Pelosi they think they have reason not to — mainly because they invited her to China in 1991 and then she went to Tiananmen Square.”

Pelosi has also been a strong defender of Chinese dissidents, including championing legislation that provided a pathway to US citizenship for students who were trying to escape from repression in China.

Wei Jingsheng, a prominent Chinese dissident who was persecuted for calling for democracy in China and has dealt repeatedly with Pelosi since being expelled by Beijing, said her “key asset” was that she listened to dissidents.

“Over time, she has proven that she is more often right on the PRC [People’s Republic of China] than others,” said Wei, who echoed a view shared by friends and opponents that might explain Pelosi’s determination to visit Taiwan despite the warnings: “Once she makes a decision, few can dissuade her.”

One Democratic lawmaker said Pelosi was also cementing her legacy, particularly given that the 82-year-old will have to relinquish the role of Speaker if Republicans take control of the House, as expected, in November’s midterm elections.

“This is part of her farewell tour for her career, and she always wanted to go to Taiwan,” he said.

Follow Demetri Sevastopulo on Twitter