TIMELINE-Key events in Hong Kong's squeeze on Tiananmen crackdown commemorations

By Jessie Pang and James Pomfret

HONG KONG, Jan 22 (Reuters) - Hong Kong's High Court will begin on Thursday a landmark subversion trial of the leaders of a group that once organised annual commemorations of Beijing's Tiananmen Square crackdown on student-led pro-democracy protests in 1989.

The vigil has been blocked since 2020, first because of COVID-19 curbs and then a national security law imposed that year following pro-democracy protests in 2019.

Chow Hang-tung, 40, the former vice-chair of the now-disbanded Hong Kong Alliance in Support of Patriotic Democratic Movements of China, and two other former Alliance leaders, Lee Cheuk-yan and Albert Ho, face up to 10 years in jail for "inciting subversion of state power" under the security law.

Following is a timeline of key events:

May 21, 1989 - The Alliance is set up by activists including Szeto Wah following a May 20 protest, when tens of thousands marched to oppose martial law in Beijing.

June 4-5 - People's Liberation Army troops fire on protesters and citizens in and around Beijing's Tiananmen Square.

A lone protester stands in front of a convoy of tanks on the Avenue of Eternal Peace close to the square, an iconic image beamed across the world.

June 4, 1989 - The Alliance helps organise a mass "sit-in" protest at Hong Kong's Happy Valley racecourse that draws about 200,000 people who condemned the bloody crackdown.

June 4, 1990 - The Alliance organises its first annual candlelight vigil in the Asian financial hub's Victoria Park, an event that drew thousands yearly for nearly three decades.

July 1997 - Hong Kong, a British colony for more than 150 years, returns to Chinese sovereignty.

2019 - Millions turn out at mass pro-democracy protests in Hong Kong, angered by Beijing's tightening grip on the city's freedoms.

June 4, 2020 - Thousands defy a police ban on COVID-19 curbs to gather with candles in Victoria Park for the anniversary, resulting in more than two dozen charged.

June 30 - China's parliament imposes a national security law on Hong Kong, drawing condemnation from the United States amid concerns it will be used to crack down on dissent.

June 3, 2021 - Chow arrested on suspicion of promoting an unauthorised assembly to mark June 4.

June 4, 2021 - Police block off Victoria Park to prevent gatherings.

Sept 8-9, 2021 - Chow, Lee, Ho and four other Alliance members are arrested under the national security law.

Sept 9, 2021 - Police raided and shut down a June 4 museum during an investigation into the Alliance.

Sept 10, 2021 - The trio are charged with inciting subversion and remanded in custody. Chow is denied bail.

Sept 25, 2021 - The Alliance members vote to disband.

Dec 13, 2021 - Eight activists including Chow are jailed for up to 14 months for organising, taking part in and inciting participation in a banned June 4 vigil.

March 11, 2023 - Chow and two former Alliance members are jailed for four and a half months for not complying with a national security police request for information.

June 4, 2023 - Hong Kong police detain 23 people for "breaching public peace" on the Tiananmen anniversary.

October 28, 2024 - The High Court bars Chow from calling overseas witnesses to testify virtually in the trial.

March 6, 2025 - Hong Kong's top court unanimously overturns the convictions of Chow and two other Alliance members in the information request case, calling it a miscarriage of justice.

Nov 3, 2025 - The High Court rejects Chow's application to terminate the trial, on grounds of prosecution accusations she called vague and insubstantial.

Jan 22, 2026 - The trial opens after several delays, and is expected to run to 75 days.