On June 4, 1989, tanks and armed soldiers surrounded Tiananmen Square in Beijing. Arriving from all directions, Chinese troops killed several hundred civilians who were blocking the streets to protect the students who had occupied the square for weeks. Soldiers opened fire when over a hundred students refused to leave, a bloody repression of China’s most important democratic movement.

For the last 30 years, the Chinese regime has never allowed an official investigation into these events. Textbooks in China ignore this piece of history altogether. The media cannot report on the Tiananmen crackdown, as the government bans publications related to the event, even in English. The topic has become China’s biggest taboo — the government censors Internet searches for “Tiananmen massacre,” “64,” “Tank Man,” and even “today.”

How did this democratic movement change China? And how has the massacre changed the Chinese people?

The Chinese regime has become more repressive since 1989

The Communist Party reshuffled the top leadership, following the suppression of dissidents in Beijing and other major cities. Many liberal reformers were removed, replaced by conservatives. Many political reforms, such as introducing more intraparty competition, ended.

In one study, Fordham legal scholar Carl Minzner and I show that the post-Tiananmen regime in China has become more repressive, reflected in the heightened power of police chiefs and skyrocketing police spending. Over the last three decades, the Chinese domestic security apparatus expanded dramatically. “Stability maintenance” — a government euphemism for repressing collective protests — became a top priority for local Chinese authorities.

Government authorities harass, detain and arrest individuals they deem a threat to the regime and vast numbers of government and informally recruited personnel keep watch over selected political dissidents, citizen activists and public interest lawyers. The recent crackdown on Uighurs — an ethnic minority concentrated in Xinjiang — suggests that China has almost become a police state.

Tiananmen has produced silent dissidents

Despite censorship of public discussion, research shows that government violence toward civilians in the remote past can leave a lasting scar on citizens’ political identity. Parents who witnessed violence usually tell stories to their children, so even people born long after the violence can still be affected.

My study of the violence during China’s Cultural Revolution, which took place from 1966 to 1976, shows that state repression has a long-lasting effect on whether people trust their political leaders, and how much they support the regime almost a half-century later. I analyzed the results of the 2008 Texas A&M University China Survey, which interviewed a random sample of 4,000 Chinese adult citizens. I found that the respondents who grew up in areas that witnessed more government-led killings during the late 1960s are less trusting of current national leaders and more critical of the political regime, condemning the country’s lack of democracy and freedom of expression.

One reason violence can influence people for a long time is that families talk about it. My research shows that China’s younger generation — those who did not witness the violence — are still influenced by it if their parents discuss political issues at home. Living under a repressive government, Chinese parents tell their children not to trust the country’s leaders.

My research on government repression during the Cultural Revolution also suggests that the violence has left many in China less willing to protest against the government. Having experienced or heard about government repression before, people want to play it safe by behaving loyally toward their government. But censorship of public discussions has not erased people’s memory of the repression.

The legacies are, therefore, mixed: Repression makes people resent the government, but also makes them quiet. It produces silent dissidents.

These legacies tend to last for a long time. A study by economic historians Melanie Meng Xue and Mark Koyama demonstrates that people in localities that witnessed state repression in 17th-century China still exhibit different attitudes toward the government than people in other places.

Silent dissidents might take action

While the descendants of the victims of repression tend to remain silent when the regime is strong, they take action when the government shows signs of weakness. Here’s an example. In 1944, after the Soviet Union recaptured the Crimean Peninsula from Nazi Germany, the Red Army accused all Crimean Tartars of collaborating with the Nazis and deported them to Uzbekistan. Political scientists Noam Lupu and Leonid Peisakhin surveyed the families of the direct victims of the deportation and demonstrate that, even after the fall of the Soviet Union years later, they hold hostile attitudes toward Russia and participate more in politics.

In another study, political scientists Arturas Rozenas, Sebastian Schutte and Yuri Zhukov show that the communities in Ukraine that were repressed by Stalin in the 1940s are more likely to oppose “pro-Russian” parties. Rozenas and Zhukov, in a recent study, demonstrate that when a regime cannot control society using force, victims of past repression mobilize to join mass opposition to the regime.

China’s Communist Party faces a dilemma

The Chinese Communist Party 30 years ago survived a critical challenge to its rule, but the governing structure and the society that has emerged will pose ever-present threats to the party’s survival.

My research suggests China’s expanded security regime requires significant budget allocations to police activities each year at every level of government. This diverts funding away from productive and welfare-enhancing programs, such as education and health care.

What’s next for China? Economist Timur Kuran noted an “element of surprise” in the East European revolution of 1989: Everyone seemed loyal to the regime until they suddenly joined the revolution. The silent dissidents in China might be a source of surprise if the Chinese regime cannot sustain its high coercive power.

Yuhua Wang (@YuhuaWang5) is an assistant professor in the department of government at Harvard University and author of “Tying the Autocrat’s Hands: The Rise of the Rule of Law in China” (Cambridge Studies in Comparative Politics).