This report, originally published in May 2020, has been updated.

“The end of Hong Kong that the world knew before.”

That’s how pro-democracy activist Joshua Wong described the passage of Hong Kong’s national security law a year ago. When Chinese President Xi Jinping signed the sweeping legislation, which gave Beijing the legal ammunition to effectively criminalize dissent in the city, the impact descended swiftly. Twitter users deleted their accounts. Political parties disbanded. Pro-democracy posters were stripped from restaurant walls.

A year later, critics of the law have seen their fears materialize. Wong is in prison. Dozens of protesters and journalists have been arrested, while others have fled the country. As the space for free expression shrank, media outlets shut down or self-censored. School curriculums were rewritten. China has used the threat of punishment under the law to further cement its grip on the territory.

Here’s a look at how the first year of life under the national security law played out.

What degree of autonomy did Hong Kong have?

In July 1997, Britain and China signed an accord granting Hong Kong relative autonomy for at least 50 years. It was the culmination of more than a century of competition between London and Beijing over the city.

The agreement allowed Hong Kong to operate under semiautonomous rule — with separate legal, political and economic systems from mainland China — and a de facto constitution, called the Basic Law, intended to protect liberties such as freedom of the press and assembly. When Britain handed over the former colony, China pledged to preserve the “one country, two systems” framework through 2047.

For two decades, Hong Kong flourished as a global financial center while running many of its own affairs.

China continued to view Hong Kong as part of its territory, however, and since Xi took over leadership of China’s ruling Communist Party in 2012, he has repeatedly meddled with Hong Kong’s special status.

Although Hong Kong has its own legislature, its chief executive is not elected directly but chosen by a committee. Opponents of the system say China continues to exert undue control over that process.

China previously tried to push a security law in 2003, but the legislation was abandoned in the wake of mass protests.

In 2014, a pro-democracy campaign drew more than 1 million people to Hong Kong’s streets. It would come to be known as the “Umbrella Movement,” after the umbrellas protesters carried to protect themselves from tear gas. The protests lasted 79 days but were ultimately quashed, leaving many young people feeling disenfranchised from the city’s political system.

In 2019, protests again broke out over concerns that Hong Kong would pass a bill allowing for extradition to China. Opponents of the measure feared it would be used to crack down on anti-Beijing activists. The demonstrations lasted months, at times turning violent, and police faced accusations that they used excessive force on protesters.

Chief Executive Carrie Lam eventually pulled back the bill, but the protests had ballooned into a movement centered on a broader set of democratic demands. Chinese and Hong Kong authorities argued that a national security law was necessary to return “stability” to the territory.

What is the national security law?

The law’s provisions proved harsher than many had feared. Under the new rules, a maximum life sentence can be handed out to anyone found guilty of “separatism,” “subversion,” “terrorism” or “collusion with foreign forces.” The definition of terrorism includes acts of vandalism such as those carried out by protesters during demonstrations in recent years.

The legislation offers more leniency toward those who agree to provide information about others. It paved the way for Beijing to open a new national security office in the city, employing mainland agents.

The law also allows for the staffing of a new magistrate court and law enforcement agencies with Chinese authorities, and increased police authority to “intercept communications and covertly surveil persons reasonably suspected of crimes against national security.”

How has the law been used, and what response has it met?

The first prominent arrests under the law were made in late July 2020, when authorities in Hong Kong arrested four people between the ages of 16 and 21, saying they were suspected of inciting secession. Police cited comments they made on social media, rattling residents who feared the new law would significantly limit freedom of speech.

Dozens were detained for running in or helping to facilitate a primary vote in July 2020 to pick pro-democracy candidates to run in legislative elections scheduled for September. The elections were ultimately postponed, and many of the pro-democracy candidates were barred from running.

The law has also given officials cover to crack down on news outlets. In August, authorities raided the newsroom of pro-democracy newspaper Apple Daily, founded by media tycoon Jimmy Lai in 1995. Lai, his sons and several executives of the newspaper’s parent company, Next Digital, were arrested. Lai received two prison sentences this spring that add up to 20 months, and his assets were frozen in May.

Police raided the paper’s newsroom again in June, arresting its top executives and scouring journalists’ notes. Under pressure, the daily shut down operations last week.

Facing visa denials and legal threats, foreign news outlets have moved staff out of Hong Kong.

Many Hong Kong people have relocated to Britain, Canada and other countries since the law was passed. Others, lacking passports, have attempted to escape to Taiwan by boat, with mixed success.

For those who remain, Beijing is using the law to rewrite history and push for a new generation of obedient subjects. Publishers are revising textbooks to fall in line with the Chinese government’s preferred narrative. Museums are under renovation. Beijing has set up a new “propaganda” division in the city.

Commemorations of the 1989 Tiananmen Square massacre — long a sign of Hong Kong’s independence — were outlawed.

How has the United States responded?

In May 2020, Secretary of State Mike Pompeo told lawmakers he viewed Beijing’s push for the law as “the latest in a series of actions that fundamentally undermine Hong Kong’s autonomy and freedoms.”

“No reasonable person can assert today that Hong Kong maintains a high degree of autonomy from China, given facts on the ground,” he said at the time.

The announcement to Congress signaled a sharp shift in the U.S. trade relationship with the city. Hong Kong’s relative autonomy had allowed the city to maintain a special status that left it exempt from tariffs the United States has placed on China.

President Donald Trump later announced the United States would no longer treat Hong Kong and China separately on major issues including trade and extradition. The Biden administration has continued that policy.

In June 2020, the State Department implemented new visa restrictions on current and former Chinese Communist Party members linked to clampdowns on Hong Kong’s freedom.

In August 2020, the Trump administration imposed sanctions on 11 Hong Kong officials, and the Biden administration sanctioned 24 officials in China and Hong Kong in March in response to Beijing’s overhaul of electoral rules in the territory.

How else has China cemented control?

As the city recovered from the initial wave of the coronavirus pandemic, Beijing sought new ways to tighten its grip. In May 2020, in a major escalation, pro-Beijing lawmakers took over a committee that controls the city’s legislative agenda, with plans to push against dissent. In December, Hong Kong’s highest court unanimously ruled in favor of a government law banning masks at protests.

In March, China passed electoral rules for the territory that will ensure pro-Beijing “patriots” govern Hong Kong.

Gerry Shih in Seoul and Shibani Mahtani in Hong Kong contributed to this report.