The Chinese government’s paranoia about overseas dissidents can seem strange, considering the enormous differences in power between exiled protesters who organize marches in America and their mighty homeland, a geopolitical and economic superpower whose citizens they have almost no ability to mobilize. But to those familiar with the Chinese Communist Party, the government’s obsession with dissidents, no matter where in the world they are, is unsurprising. “Regardless of how the overseas dissident community is dismissed outside of China, its very existence represents a symbol of hope for many within China,” Wang Dan, a leader of the Tiananmen Square protests who spent years in prison before being exiled to the United States in 1998, told me. “For the Chinese Communist Party, the hope for change among the people is itself a threat. Therefore, they spare no effort in suppressing and discrediting the overseas dissident community — to extinguish this hope in the hearts of people at home.”

To understand the party’s fears about the risks posed by dissidents abroad, it helps to know the history of revolutions in China. “Historically, the groups that have overthrown the incumbent government or regime in China have often spent a lot of time overseas and organized there,” says Jessica Chen Weiss, a professor of China studies at Johns Hopkins University. The leader Sun Yat-sen, who played an important role in the 1911 revolution that dethroned the Qing dynasty and led eventually to the establishment of the People’s Republic of China, spent several periods of his life abroad, during which he engaged in effective fund-raising and political coordination. The Communist Party’s own rise to power in 1949 was partly advanced by contributions from leaders who were living overseas. “They are very sensitive to that potential,” Weiss says.

“What the Chinese government and the circle of elites that are running China right now fear the most is not the United States, with all of its military power, but elements of unrest within their own society that could potentially topple the Chinese Communist Party,” says Adam Kozy, a cybersecurity consultant who worked on Chinese cyberespionage cases when he was at the F.B.I. Specifically, Chinese authorities worry about a list of threats — collectively referred to as the “five poisons” — that pose a risk to the stability of Communist rule: the Uyghurs, the Tibetans, followers of the Falun Gong movement, supporters of Taiwanese independence and those who advocate for democracy in China. As a result, the Chinese government invests great effort in combating these threats, which involves collecting intelligence about overseas dissident groups and dampening their influence both within China and on the international stage.

Controlling dissidents, regardless of where they are, is essential to China’s goal of projecting power to its own citizens and to the world, according to Charles Kable, who served as an assistant director in the F.B.I.’s national security branch before retiring from the bureau at the end of 2022. “If you have a dissident out there who is looking back at China and pointing out problems that make the entire Chinese political apparatus look bad, it will not stand,” Kable says.

The leadership’s worries about such individuals were evident to the F.B.I. right before the 2008 Beijing Olympics, Kable told me, describing how the Chinese worked to ensure that the running of the Olympic flame through San Francisco would not be disrupted by protesters. “And so, you had the M.S.S. and its collaborators deployed in San Francisco just to make sure that the five poisons didn’t get in there and disrupt the optic of what was to be the best Olympics in history,” Kable says. During the run, whose route was changed at the last minute to avoid protesters, Chinese authorities “had their proxies in the community line the streets and also stand back from the streets, looking around to see who might be looking to cause trouble.”