As buses and vehicles burn, pro-democracy demonstrators retreat down Changan Avenue as soldiers advance towards the square. Credit:Getty Images Museum organisers say about half of its daily visitors are from the mainland, where information about the events of June 4, 1989, are censored. Wang observed while studying international relations at a university in Shanghai that the late 1980s were a transformative time in world events. The Berlin Wall would fall, the Soviet Union was on the verge of disintegration, yet China in 1989 “was just worth a line or two” in her textbooks. “The teachers might take you into their office and have a quiet word with you to explain some things if you asked,” she said. “But this was risky for them; it's very sensitive.”

The bodies of dead civilians lie among mangled bicycles. Credit:AP While upwards of 200,000 will cram into Hong Kong's Victoria Park for a candlelight vigil on Tuesday night, heightened security will likely snuff out any sign of public commemoration or protest in central Beijing itself. China's state security forces have warned activists, artists, journalists and intellectuals with a track record of keeping the topic alive to avoid the taboo topic – arresting those who fail to comply. High-profile rights lawyer Pu Zhiqiang and academic Xu Youyu were among five detained for attending a private discussion forum on May 3. Outspoken 70-year-old journalist Gao Yu, who has already been jailed twice for her writings on Tiananmen Square, was arrested in late April for “leaking state secrets”, while Xin Jian, a Chinese researcher for a Japanese newspaper, and Wu Wei, a former South China Morning Post reporter, have also been detained for weeks.

Other activists, as is common for politically sensitive periods, have been taken out of Beijing or, like Ding Zilin of Tiananmen Mothers, barred from re-entering the capital. Meanwhile, princeling sons and daughters of liberal-leaning Communist Party elders, have also been called to have “tea” if they are found to have said something deemed inappropriate. It has amounted to a particularly tense period in central Beijing, with security forces also on terror alert after a spate of deadly attacks stemming from ethnic divisions in China's far-western Xinjiang province. Paramilitary officers wielding automatic weapons are patrolling major intersections and government buildings in open-air jeeps, police vehicles installed with Google Earth-style cameras circulate the capital, and beefed-up security measures at some subway and train stations are causing lengthy delays. “It's a harsh year, the harshest of all the major anniversaries,” says Lee Cheuk-Yan, a Hong Kong legislator and chairman of the Hong Kong Democratic Alliance, which raised the funds for the museum. “Compared to the 15th anniversary, 20th anniversary – this is the worst year.” “In many ways there has only been regression on human rights, no progression on political reform and, under Xi Jinping, they are only more repressive than in the past.”

The Tiananmen demonstrations were triggered in April 1989 by an outpouring of grief over the death of the popular reformist Communist Party leader Hu Yaobang, two years after he had been ousted. Student leaders called for democracy, free speech, workers' rights, and an end to nepotism and corruption. “It was a genuine, spontaneous movement from the people out of total devotion to the future of the country,” says Willy Lam, a politics professor at the Chinese University of Hong Kong, who covered the Tiananmen Square demonstrations as a Beijing-based reporter for the South China Morning Post in 1989. “It was a beautiful movement of people taking quite a risk, even though of course nobody actually expected the soldiers to shoot to kill." After initially taking a conciliatory tone, paramount leader Deng Xiaoping declared martial law, and hundreds of thousands of troops were mobilised. When the protesters refused to budge, the order to vacate the square by force was given. “Right until they started shooting, students and ordinary citizens remained defiant,” Lam says. “The great majority of people I spoke to did not believe they would use live ammunition.” Most of the deaths actually occurred on the Beijing roads leading to the square – student leaders at the square agreed to stand down at the last minute to prevent further bloodshed.

China says the protests were “counter-revolutionary” and has never confirmed a death toll. Estimates range from a few hundred to more than 2000. In Hong Kong, the June 4 candlelight vigil is taking on greater symbolism and significance beyond a major milestone anniversary. Calls for Beijing to honour its promise of allowing Hong Kong universal suffrage in 2017, 20 years after the handover from British colonial rule, are becoming louder and more anxious, underlined by a fundamental fear of their current freedoms being eroded. With mainland Chinese interests connected to the Communist Party having greater influence in Hong Kong's media and politics, there is arguably the greatest levels of apprehension in the special administrative region since the 1997 handover, or the 2003 attempt to rewrite Hong Kong's national security laws. The indications are that Beijing has a different idea to what universal suffrage might mean. Concerns are high that Beijing will seek to control the nomination of all candidates, by stacking a proposed nomination college – through which candidates have to be selected - with those sympathetic to the Communist Party.

Tensions have also bubbled between ordinary Hong Kongers and the ever-increasing numbers of mainland Chinese visiting and working in Hong Kong, with the latter blamed for everything from inflating property prices, crowding out scenic hotspots, being rude on subway trains, and relieving themselves in the street. Above all, Hong Kongers feel they have this one chance at getting their shot at democracy right. “If we fail to achieve the goal for 2017, it is difficult to say when we would obtain another timetable for universal suffrage," chief secretary Carrie Lam said in March. Timothy Lee, 22, a former student union president at the City University of Hong Kong, said teenagers were becoming more and more concerned about their society, and that the Chinese government's crackdown and censorship of June 4 only served to remind them to cherish their freedom. “It's our responsibility,” he says. “We are university students too and we need to remember the truth. We will go to the June 4 [commemoration] and tell the Chinese government that Hong Kong people, and especially Hong Kong youngsters will not forget that night.” Activists organising Hong Kong's Occupy Central civil disobedience movement are preparing for a "trial run" in early July – a sit-in blocking the roads of the city's central business district, emboldened by Taiwan's Sunflower movement that saw tens of thousands of student protesters occupy Taipei's legislative yuan in March and April.

The Sunflower protests stemmed from the Nationalist Kuomintang government's attempt to ratify a trade deal with the mainland without a promised review. J. Michael Cole, a Taiwan-based journalist and the editor-in-chief of Thinking Taiwan, says the protests were not simplistically anti-government, anti-China, or even anti-free trade, but stemmed from a desire to erect “the last line of defenceagainst an insidious process of de-democratisation”. “While Beijing has sought to erode the quality of Taiwan's democracy in order to facilitate eventual unification and lower the contradictions caused by Taiwan's integration, the Sunflower Movement has fought back on those very terms, with a heartfelt appeal for the public to pay closer attention to the quality of Taiwan's government institutions and the individuals who run their country.” The promotion of Xi Jinping, a man widely believed to have reformist credentials, to the Chinese presidency was considered by many the best opportunity for change in a decade. “Intellectuals had thought it may have been possible that the June 4 case may have been reopened and redressed,” Warren Sun, a historian at Monash University, says. “Now it's quite clear that it was false hope.”

Call it confidence, assertiveness or belligerence, but China's leadership under Xi is increasingly worrying its neighbours. It has raised the stakes in major territorial disputes with Japan, Vietnam, the Philippines and other neighbours in both the East and South China Seas. It admonished Australia for daring to question its sudden move to declare an air defence zone over the East China Sea, and blasted the United States for accusing it of state-sanctioned cyber-espionage. As Hong Kong and Taiwan fight to preserve their own freedoms and values, some extremists in the region of Xinjiang are resorting to acts of terror, having decided they've already lost that battle. All the while, Xi is staking his credibility on a game of anti-corruption whack-a-mole, while grappling with China's slowing and steeply unbalanced economy. There are many other things on the leader's plate, and redressing the most sensitive chapter of China's modern history seems more distant than ever. “The 25th anniversary is just telling us a quarter of a century has passed,” Gao Yu, the journalist, told me in an interview just hours before her arrest. “But it's not a year of breakthrough, nor a chance for China to enter democracy.” But perhaps Hu Dehua, the son of Hu Yaobang, put it best.

Loading “There was a window for reform then [in the 1980s],” he told the South China Morning Post in April. “But it was missed and I don't know when the next one will come.” *Not her real name.