BEIJING >> Dissidents silenced. Security tightened. References scrubbed from the internet.

China imposed an information lockdown Tuesday on the 30th anniversary of its bloody crackdown on pro-democracy protesters at Tiananmen Square, a stark reminder that three decades later, the possibility of democratic change has all but evaporated.

Extra checkpoints and street closures greeted tourists who showed up before 5 a.m. to watch the daily flag-raising ceremony at the square in the center of Beijing. People overseas found themselves blocked from posting anything to a popular Chinese social media site.

China has largely succeeded in wiping the events of June 3-4, 1989, from the public consciousness at home, where the anniversary of the crackdown passed like any other weekday. To Western critics, who this year included U.S. Secretary of State Mike Pompeo, China has a simple answer: Our model works.

“The Chinese government has long had a clear conclusion about the political disturbance that occurred in the late 1980s,” foreign ministry spokesman Geng Shuang said in response to Pompeo. China’s economic success “fully proves that the development path we chose is completely correct and has been firmly supported by the people.”

The seven-week-long Tiananmen Square protests and their bloody end, in which hundreds if not thousands of people are believed to have died, snuffed out a tentative shift in China toward political liberalization.

The mantra of the ruling Communist Party has become stability over all else, and the party says the stability it has delivered has been a necessary underpinning to the country’s economic growth.

For many Chinese, life is better. Incomes have risen, and social restrictions such as family size and where people can live have been loosened. It’s political freedom that remains strictly controlled.

Half a dozen activists could not be reached Tuesday by phone or text. One who could, Beijing-based Hu Jia, said he had been taken last week by security agents to the northeastern coastal city of Qinghuangdao.

Chinese authorities routinely take dissidents away on what are euphemistically called “vacations” or otherwise silence them during sensitive political times.

“This is a reflection of their fears, their terror, not ours,” Hu said.

Under current President Xi Jinping, the government has tightened control over everything from religion to the internet in an apparent bid to make the Communist Party central to the future of China.

“I don’t think that in the foreseeable future there is the possibility for another mass movement against the regime, because the system of control is so complete,” said Andrew Nathan, a professor of Chinese politics at Columbia University.

Chinese overseas reported on Twitter that they were blocked from posting on Weibo, a popular social networking site. Weibo did not respond to phone and email requests for comment.

Even those who know what happened 30 years ago are reluctant to talk about it in public. A 24-year-old designer said last week in Beijing that he thought it was quite a pity when he learned that many had died.

“But it’s really not convenient to talk about it,” he said, giving only the name he goes by in English, Tony.

Any commemoration of the event is not allowed in mainland China, though tens of thousands turned out for an annual candlelight vigil in Hong Kong. The Chinese territory has relatively greater freedoms than the mainland, though even there, activists are concerned about the erosion of those liberties in recent years.

Pompeo issued a statement Monday saluting what he called the “heroes of the Chinese people who bravely stood up thirty years ago … to demand their rights.” He said that U.S. hopes that China would become a more open and tolerant society have been dashed.

He and his European Union counterpart Federica Mogherini urged China to come clean on what happened and how many died.

“Acknowledgement of these events, and of those killed, detained or missing in connection with the Tiananmen Square protests, is important for future generations and for the collective memory,” Mogherini said in a statement.

Geng, the foreign ministry spokesman, said that “some people in the U.S. always regard themselves as others’ teachers and interfere in other countries’ internal affairs under the guise of so-called democracy and human rights, while turning a blind eye to problems at home. The Chinese people have seen through their hypocrisy and sinister intentions.”

The crackdown set the Communist Party on a path of repression, Nathan said, adding that China would likely be a very different place if the nation’s rulers had ended the protests peacefully through dialogue instead of by force.

“They embarked on a strategy of not dialoguing with the people,” he said. “The party knows best, the party decides, and the people have no voice. So that requires more and more intense repression of all of the forces in society that want to be heard.”