The first threatening phone call that Zhuang Liehong got in New York was in the fall of 2016, on a gloriously warm September morning. The call came from a jail where his father was being held following a protest in Mr. Zhuang’s home village in Southern China. “Is this Zhuang Liehong?” asked an unfamiliar voice. When Mr. Zhuang said yes, there was a pause and his father’s voice came on the line. “Son,” he said, “stop doing what you’re doing. It will be bad for your family.”

What Mr. Zhuang had been doing, for the most part, was posting on Facebook. He was putting up photos that had been sent by friends and family, which recorded a police crackdown that had swept his home village, Wukan. Five years earlier, during the fall of 2011, Mr. Zhuang had been a ringleader in a series of protests that overtook the little seaside village. He had helped alert his fellow villagers to land grabs that were chipping away at village boundaries and filling the pockets of local officials. When those protests ended, it seemed the villagers had emerged victorious. Villagers had been granted the right to hold local elections, and Mr. Zhuang was one of seven new village committee members tasked with administrating the village and returning stolen land.

Back then, Wukan was held up among democracy activists as a symbol of liberalization, a hopeful sign that China was open to political change. But the elections were misleading, the hope misplaced. Mr. Zhuang fled to New York in 2014. Two years later, he found himself answering that phone call in New York City, swept up in new political currents. The Communist Party of China was taking a recent crackdown on dissent and moving it over borders. Mr. Zhuang had moved to the United States to speak freely about his village. In his father’s voice he heard the ventriloquism of the corrupt officials who had sold off his village land. Mr. Zhuang guessed that his father was surrounded by security personnel. He felt the phone call suggested a trade — his father’s freedom for Mr. Zhuang’s silence.

Since 2015, a sweeping crackdown on internal dissent has ensnared hundreds of human rights lawyers, feminists, journalists and democracy activists. China now spends more on internal security than it does on its military. And as the crackdown continues at home, the Chinese Communist Party has started to expand its reach, looking to enforce censorship, increase surveillance and silence dissent across borders. Their targets have included academics, exiled business elites, former judges and activists like Mr. Zhuang.