Will President-elect Donald Trump’s vow to “launch the largest deportation program in American history” truly keep millions of immigrants out of the country? My research on deportees over the last five years suggests it won’t.

Here’s why: They’ll come back.

One of the migrants I interviewed was deported to a perilous town in northern Mexico, where he found himself in immediate danger on arriving at a bus terminal. Members of a criminal group demanded that he provide a contraseña — a password he didn’t have — or face kidnapping. He ultimately borrowed $1,500 from a friend to pay them off, remain free and make his way back to the United States.

His experience is an example of the risks deportees face in their countries of origin. Those dangers — and the relative safety of the only homes they have — often motivate them to undertake harrowing journeys back to the United States.

Although data on deportees is somewhat limited, the evidence we have shows that people re-immigrate after deportation more frequently than many might expect. In fiscal 2020, for example, the federal government classified 40% of deportations as “reinstatements of removal,” meaning the deportees had reentered the United States after being removed or ordered to leave. A 2019 report by the American Immigration Council, a pro-immigration advocacy group, similarly noted that such reinstatements of removal generally make up 40% of deportations annually. From 2011 to 2020, approximately 1.3 million deportations affected people who had been deported before.

That’s because deportation policies are at best blunt instruments that take little account of the human lives they ensnare. Those who view mass deportation as a solution to unauthorized immigration ignore the deep roots, sense of belonging, family ties and resolve that drive people back to the country they call home.

Undeterred by deportation, people I’ve interviewed have found ways to return to the United States with or without permission. Their stories reveal the rarely discussed truth that deportation is not necessarily the end of migration; it is often a temporary, futile interruption.

I spoke to another man who was born in Mexico but raised in the United States, served in the military and struggled with post-traumatic stress. Because of a minor cannabis possession charge, he was deported to a country he barely remembered. In 2021, more than a decade after his exile, he returned to the only land he considers his own, the United States.

“You can travel the world,” he told me, “but eventually, your heart and spirit will call you home.”

Another Mexican-born, U.S.-raised military veteran I interviewed was also deported over a marijuana charge. Feeling “erased from existence,” he risked his life to return less than a month later.

“I don’t need a paper to tell me I’m an American,” he told me.

These stories expose a fundamental flaw of mass deportation. In contrast to the cyclical migration patterns of earlier decades — when migrants, mostly men, moved back and forth between the United States and Mexico with relative ease in response to the labor market — today’s cycle is driven by government coercion and unbreakable bonds. Forced departures lead to inevitable returns as deportees are pulled back by connections that no amount of enforcement can sever.

The coyotes who smuggle them have become part of what the anthropologist Jason De León calls a “border-security-industrial complex.” If their illicit businesses were publicly traded, their stocks would be soaring on renewed demand. Meanwhile, border enforcement policies push migrants into treacherous terrain where they face dehydration, hypothermia and death in the desert.

For deportees, returning is an act not just of determination, but of survival. Some are lucky enough to make it back, but as the Spanish saying goes, “Tanto va el cántaro al agua hasta que se quiebra”: The pitcher goes to the well until it finally breaks. Deportation policies push people to take increasingly greater risks to return to the only homes they’ve ever known. The next attempt could always be their last.

Deportation may well become the defining issue of our era if we continue down this punitive path. When mass deportations fail, what will follow? Will we see modern-day versions of Franklin D. Roosevelt’s executive order authorizing forced removal and incarceration of Japanese Americans, complete with “relocation centers”?

Under a very different executive order signed by President Biden in 2021, the Homeland Security and Veterans Affairs departments prioritized the return of deported U.S. military members and their families. The Deferred Action for Childhood Arrivals program, known as DACA, similarly sought to recognize longtime residents’ ties to the country and restore their place in the American communities they call home.

Such policies live up to American ideals of justice and inclusion by embracing those who, in every meaningful way, already belong. Mass deportation would betray those values, put even more lives at risk and very often fail on its own terms.

Saúl Ramírez is a fellow at Harvard Law School and a doctoral candidate in sociology at Harvard.