The demonstrators are less idealistic than in 2014, and the police respond more forcefully

At the end of pro-democracy protests that paralysed central Hong Kong for 79 days in 2014, demonstrators left behind glitter bombs and stickers with the outline of an umbrella and the message: “We’ll be back.”

More than four years later, they have made good on that promise. Since Tuesday evening, thousands of protesters have poured into the streets, surrounding their government. They blocked roads, built barricades, and occupied many of the same areas that were under siege during the Occupy protests, also known as the “umbrella movement”, a campaign for “genuine democracy” in elections. Like in 2014, they have clashed with riot police and suffered rounds of teargas.

Quick guide What are the Hong Kong protests about? Show Hide Why are people protesting? The protests were triggered by a controversial bill that would have allowed extraditions to mainland China, where the Communist party controls the courts, but have since evolved into a broader pro-democracy movement. Public anger – fuelled by the aggressive tactics used by the police against demonstrators – has collided with years of frustration over worsening inequality and the cost of living in one of the world's most expensive, densely populated cities. The protest movement was given fresh impetus on 21 July when gangs of men attacked protesters and commuters at a mass transit station – while authorities seemingly did little to intervene. Underlying the movement is a push for full democracy in the city, whose leader is chosen by a committee dominated by a pro-Beijing establishment rather than by direct elections.

Protesters have vowed to keep their movement going until their core demands are met, such as the resignation of the city’s leader, Carrie Lam, an independent inquiry into police tactics, an amnesty for those arrested and a permanent withdrawal of the bill. Lam announced on 4 September that she was withdrawing the bill. Why were people so angry about the extradition bill? Beijing’s influence over Hong Kong has grown in recent years, as activists have been jailed and pro-democracy lawmakers disqualified from running or holding office. Independent booksellers have disappeared from the city, before reappearing in mainland China facing charges. Under the terms of the agreement by which the former British colony was returned to Chinese control in 1997, the semi-autonomous region was meant to maintain a “high degree of autonomy” through an independent judiciary, a free press and an open market economy, a framework known as “one country, two systems”. The extradition bill was seen as an attempt to undermine this and to give Beijing the ability to try pro-democracy activists under the judicial system of the mainland. How have the authorities responded? Beijing has issued increasingly shrill condemnations but has left it to the city's semi-autonomous government to deal with the situation. Meanwhile police have violently clashed directly with protesters, repeatedly firing teargas and rubber bullets. Beijing has ramped up its accusations that foreign countries are “fanning the fire” of unrest in the city. China’s top diplomat Yang Jiechi has ordered the US to “immediately stop interfering in Hong Kong affairs in any form”. Lily Kuo and Verna Yu in Hong Kong

But Occupy 2.0, as the latest protests have been called, is different in key ways. Today’s protesters are a lot less idealistic and a lot more cynical. And they are pushing for a specific goal: the cancelling of a proposed extradition bill that would allow Beijing to extradite alleged criminals from Hong Kong, a territory of China that is meant to operate with a high degree of autonomy with its own legal and judicial system, a free press, and unfettered internet.

China says the new law is to combat crime and will not be used for political ends. But critics say it will amount to the “legalised abduction” of activists, dissidents, and other critics of the Chinese regime, for whom Hong Kong has long been a base.

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Over the past four years since the umbrella protests ended, the Hong Kong government has jailed activists, disqualified elected pro-democracy lawmakers, and constructed expensive infrastructure physically linking Hong Kong more closely to the mainland, while Chinese security has abducted independent booksellers in the territory.

“This is basically an accumulation of pent-up anger now boiling over,” said Victoria Hui, an associate professor of political science at Notre Dame University in the US, who follows Hong Kong politics. “It’s not just about this [law]. It’s the combination of all the things Beijing has done to erode Hong Kong’s freedom.”

Support for the protests may be broader than it was in 2014. Hundreds of businesses, as well as teachers and parents across the city, boycotted work and class on Wednesday. On Sunday, an estimated 1 million marched against the bill, which is opposed by lawyers, judges, investment bankers and churches. Many have described the fight against the extradition bill as the city’s “last battle” for its freedom and distinct identity from China.

Facebook Twitter Pinterest Police advance towards protesters during a rally. Photograph: Dale de la Rey/AFP/Getty Images

In some ways, Hong Kong’s protesters today are better equipped. On Tuesday night and Wednesday ahead of a morning debate in the legislature over the bill, they mobilised supplies – food, water, first aid kit, as well as face masks and umbrellas to shield against teargas – and passed them to those at the frontline facing off with police. Seeing protesters surrounding the government complex, officials postponed the meeting, marking a win for the demonstrators.

The authorities are more savvy now too. Wary of allowing protesters to dig in and occupy the city centre again, police have acted earlier and more forcefully: charging, teargassing, and firing rubber bullets. Angry protesters threw construction materials at police and jeered at them. In at least one case, according to videos posted online, police beat a protester with batons. Broadcaster RTHK reported that 72 had been taken to hospital, two of them in a serious condition. Police succeeded in clearing protesters from the areas around the legislative complex.

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Today, both Hong Kongers and the international community have hardened in their views of Beijing, which remains locked in disputes with the US and other countries over trade, Huawei, and human rights. The extradition bill is exacerbating those tensions.

The US, the UK, Canada and others have all criticised the extradition bill and Beijing has in response blamed “foreign forces” for misleading Hong Kongers and attempting to destabilise China. Before the march in Hong Kong, several foreign news sites, including the Guardian, several US publications and the Toronto Star were blocked in mainland China.

In Hong Kong, despite the outpouring of opposition, few believe the bill will actually be shelved. Beijing has reiterated its support for the law and Hong Kong’s chief executive, Carrie Lam, has pledged that she will continue to push it forward.

“Even when people power cannot stop the bill, they want to show to the world, Carrie Lam, Beijing … that we care, that we won’t go down without a fight,” said Hui.