Daily news updates from Hong Kong have kept the world well briefed on the ongoing marches and demonstrations sparked by a controversial extradition bill earlier this spring. Hundreds of thousands of Hong Kongers have turned out to protest the measure, as well as the police crackdown.

What people in mainland China see is something altogether different. For the past 11 weekends, Hong Kong streets have been filled with protesters. These have largely been peaceful, decentralized and self-organized marches. But China’s state media and social media portray extremely violent demonstrations, plotted by “foreign hostile forces” including House Speaker Nancy Pelosi and the CIA.

Why, and how, does China have this alternative narrative on Hong Kong? Here’s what you need to know.

Topics about sovereignty get the highest censorship.

Hong Kong is a semiautonomous region of China, under a “one country, two systems” arrangement. The Basic Law gives Hong Kong residents “freedom of speech, of the press and of publication; freedom of association, of assembly, of procession and of demonstration,” among other rights. Although none of the demands made by the protesters mentions independence, Beijing condemns the movement as challenging Chinese sovereignty in Hong Kong. For Chinese officials, this crosses a red line.

My dissertation research on Chinese media positions on different issues suggests Beijing keeps tight control over any topic that relates to sovereignty and territorial integrity. In China, there can be only one voice — defending China’s sovereignty and national interests.

I examined news topics related to independence movements in Tibet, Xinjiang and Taiwan, as well as the territorial disputes over the Diaoyu/Senkaku Islands and the South China Sea. I also looked at social movements in Hong Kong, including the 2014 Umbrella Movement and the current protests. For China, all of these events fall in this category, subject to the highest level of censorship.

China’s propaganda system not only censors information, but it also proactively produces and disseminates information. Here’s an example. While silent on allegations of excessive force from the Hong Kong police, China’s state media cherry-picked cases in which police officers were hurt and amplified the disruption to the city.

The state television network even spread fake news that the woman allegedly blinded by a police beanbag projectile was actually shot by a protester, using a quickly debunked photo to suggest that the woman accepted money for participating in the protests.

The official narrative in China blames foreign forces for inciting “riots” in Hong Kong. This explanation may sound absurd, but it fits into the familiar rhetoric of 100 years of foreign humiliation in China’s history textbooks.

Nationalism is a common theme.

Propaganda in China has become increasingly participatory in the social media era. Party organs such as the Communist Youth League and official media such as the People’s Daily often invite Internet users to contribute to the propaganda campaigns. For example, after Hong Kong protesters threw a Chinese flag into the sea on Aug. 3, China’s state media called on Weibo users to repost the national flag with the hashtag “1.4 billion national flag protectors.”

It’s not just China’s official media promoting the narrative of violence and foreign plots. A large group of social media accounts managed by private start-up companies in China are actively participating in the propaganda campaign on Hong Kong. Most likely, these companies follow the official narrative to protect their political safety and commercial interests.

Studying viral content on Chinese social media, I find nationalistic posts are shared significantly more often than other types of content. Previous research suggests content that evokes anger and anxiety is more likely to go viral. In the specific context of China, nationalistic content that often highlights foreign hostility and threats to national interests helps social media accounts gain more traffic and followers, which result in more advertising revenue for the start-up companies.

Fact-checkers face an uphill battle.

Despite the dominance of the official narrative, some people in China are trying to fact-check popular articles and provide a more comprehensive picture of the movement. For example, they debunked Chinese news reports that Hong Kong protesters had broken the finger of a police officer with pliers. They also write long articles to explain the real factors behind the protests.

Chinese propaganda authorities censor these articles heavily. In recent weeks, they deleted some accounts that posted these types of articles. But these fact-checking articles manage to reach a certain population in China, largely through private and group sharing networks.

Reading a fact-checking article does not guarantee the reader will reject the official narrative, however. Studies in the United States have found political identity influences how one perceives the credibility of fact-checkers. Just as Republicans may be reluctant to accept a fact-checking article that is advantageous to the Democratic Party, Chinese readers with strong nationalist inclinations are likely to rebut an article that suggests Hong Kong protesters are not as violent as the Chinese media portray.

Similarly, a number of Chinese students studying abroad have chosen to trust Beijing’s narrative, despite access to multiple uncensored information sources. They have recently rallied in Sydney, London, and other cities around the world to support Beijing, and clashed with Hong Kong activists. Prior research suggests the strong nationalistic sentiments of Chinese students are partly driven by the concern that any criticism targeted at their government could also hurt the Chinese people.

Overall, the propaganda campaign in mainland China about the Hong Kong protests seems to work very well for the Communist Party — maybe too well. Some angry nationalists in China are eagerly calling for military intervention in Hong Kong, despite the fact that this would involve very high potential costs.

But previous research suggests nationalist protests in China may backfire if the regime is unwilling to fulfill protest demands. The same logic holds true for China’s online propaganda campaigns.

Kecheng Fang is an assistant professor at the School of Journalism and Communication, the Chinese University of Hong Kong.