China has detained dozens of people and launched an unprecedented security operation in central Beijing to stop anyone commemorating the 25th anniversary of an event that has been virtually wiped from the collective memory of the nation.
A quarter of a century after the People's Liberation Army turned its tanks and guns on the people and marched into Tiananmen Square on the night of June 3 and early hours of June 4, 1989, any mention of the massacre of hundreds, perhaps thousands, of people is banned from public life.
More than 50 people, including activists, lawyers, journalists and relatives of students killed in the massacre, have been detained, arrested or simply "disappeared" in recent weeks because of their efforts to commemorate the anniversary, according to human rights groups.
Most of these people have been charged with amorphous crimes that are often used to silence critics of the regime – such as "picking quarrels and provoking troubles" – and could face several years in prison if convicted.
Some were detained after holding small private gatherings in their own homes, the first time this has happened according to activists.
The crackdown highlights how potent the traumatic events of 1989 remain in Chinese politics, and how fearful the authorities are of those they fear might use those events to call for greater liberty and political participation.
Liu Xiaobo, the Nobel Peace Prize laureate who was a key figure in the Tiananmen Square student democracy protests, has been serving an 11-year prison sentence since 2009 for advocating peaceful political reform.
Several foreign governments and international bodies have expressed concern over the crackdown.