The Biden administration repatriated more than 500 Chinese nationals in the last year, laying the groundwork for systematic deportations across the Pacific Ocean.

On Friday, a large-scale deportation flight landed in China, the fifth such flight chartered by the Department of Homeland Security (DHS) since June, when the high-volume flights re-started after a lull that started in 2018.

“The Chinese nationals removed this week to the People’s Republic of China (PRC) add to the hundreds who have been removed for not having a legal basis to remain in the U.S.  This is the fourth such removal flight that we have arranged with officials from the PRC,” said Homeland Security Secretary Alejandro Mayorkas in a statement.

Collaboration on deportations has been a testy issue between China and the United States for years.

Tensions between the two superpowers have ebbed and flowed on a range of issues including trade and Taiwan, making it at times more difficult to cooperate on unauthorized migration, an issue where both countries share some common interests.

For the United States, a country where border encounters are a core political liability, the ability to quickly remove foreign nationals — and to advertise those removals — is paramount.

China has an interest in reducing emigration both to maintain a young workforce and to protect its global image as an economic superpower.

But the two countries have at times butted heads on how to address their shared goal of reducing irregular migration.

In 2020, the United States designated 13 nations, including China, as “recalcitrant countries” that refused to take back their nationals at the pace DHS wanted them removed.

The U.S. has a relatively well-equipped toolbelt to push recalcitrant countries to cooperate with removals, including visa restrictions that can be crippling for smaller countries on the list, such as Cuba.

Those sanctions are less effective for a country the size of China, though Chinese nationals compose a relatively small sliver of the population of unauthorized migrants encountered at the U.S.-Mexico border.

But encounters with Chinese nationals rose significantly between fiscal 2022 and 2024.

From October 2021 to September 2022, DHS officials encountered 2,176 Chinese nationals at the Southwest border. In fiscal 2023, that number jumped to 24,314 and in fiscal 2024, officials registered 38,246 such encounters.

Last July, Rep. Chip Roy (R-Texas) led a group of Republicans in a letter demanding Mayorkas explain the high number of arrivals and — at the time — low number of removals.

According to DHS officials, the largest obstacles to streamlined flights to China were bureaucratic difficulties in obtaining identification and travel papers for removable Chinese nationals.

A decade earlier, Obama administration officials encountered similar obstacles under then-Secretary Jeh Johnson.

Under Mayorkas, DHS officials and their Chinese counterparts hashed out agreements to speed up issuance of travel documents with the goal of setting up a standard operating procedure, both for the charter flights and the possibility of deportations on commercial flights.

And DHS officials are taking victory laps, linking the deportation flights to reduced encounters at the Southwest border; encounters with Chinese nationals have plummeted from their December 2023 high of 5,980 to 895 last November, according to Customs and Border Protection data.

“It is one element of our multi-pronged approach to border security, which has delivered border crossing levels that are lower than they were in 2019.  Our multi-pronged approach includes tough consequences for illegal border crossing, extensive engagement with foreign countries, and the development of safe and lawful pathways for people to access humanitarian relief under our laws,” said Mayorkas.

Those reduced numbers — and China’s collaboration on flights — come as President-elect Trump is due to take office, bringing a renewed emphasis on enforcement to U.S. immigration policy.

International cooperation with U.S. removals could also become more important as lawmakers push forward more draconian immigration laws like the Laken Riley Act, which if enacted would allow states to sue the federal government to stop issuing visas to recalcitrant countries, a much more serious consequence than even the most aggressive visa sanctions.

Yet immigration advocates say the deportations are not necessarily a primary factor behind reduced migration from China.

Border encounters with all nationalities have dropped across the board, from a high of 301,981 in December 2023 to 94,190 last November.

“I find it hard to believe that it’s these flights that are making that dramatic of a difference for, specifically, China,” said Tom Cartwright, an advocate for Witness at the Border who tracks DHS removal flights.

According to Cartwright, both recalcitrant and cooperative countries have seen reductions in border encounters, regardless of deportation flights.

Comparing encounters with Chinese nationals in October and November of 2023 to the same months of 2024, Cartwright found a 76 percent reduction in encounters, despite the resumption of deportation flights.

For the same time period, encounters with Guatemalan nationals dropped 73 percent even as flights dropped by 36 percent. Encounters with Nicaraguan nationals dropped 90 percent with roughly the same number of flights — six in October-November 2023, five in 2024 — and Honduran encounters dropped 79 percent despite a 42 percent reduction in flights.

“To be honest, I think there’s just a lot of other factors,” said Cartwright.