After hundreds of thousands of Mexican migrants were put on buses, planes and boats during the scorching summer of 1954 and sent across the U.S. border into often-unfamiliar parts of Mexico, the head of the Immigration and Naturalization Service declared the border “secured.”

“The so-called ‘wetback’ problem no longer exists,” Joseph Swing wrote, using a derogatory slur for Mexican migrants, in the agency’s annual report released in 1955.

But the military-style campaign, which used the same slur in its name - “Operation Wetback” - tore families apart and forcibly uprooted people in the name of securing the border, experts say. And sometimes, those efforts turned deadly.

Now, former President Donald Trump is using the Eisenhower-era operation as a blueprint for his vision, which he pledges will be “the largest domestic deportation operation in American history” to remove the estimated 10.5 million undocumented people in the United States - of whom two-thirds have lived in the country for more than a decade.

“Americans can expect that immediately upon President Trump’s return to the Oval Office, he will restore all of his prior policies, implement brand new crackdowns that will send shockwaves to all the world’s criminal smugglers, and marshal every federal and state power necessary to institute” the deportation operation, Trump campaign spokeswoman Karoline Leavitt said in a statement to The Washington Post. She added that undocumented immigrants “should not get comfortable because very soon they will be going home.”

But when describing the operation on which Trump’s plan is built, experts commonly land on the same word: “inhumane.” The Eisenhower-era operation has been referred to as such by think tanks, scholars and historians, who also said the policy was not as successful as Swing and others claimed.

Historian Kelly Lytle Hernández told The Post that the operation that was publicized in 1954 was a “racial terror campaign” that relied on scare tactics to prompt people to self-deport.

“When [Trump] harkens back to that, I think we have got to be really clear about what kind of law enforcement campaign he is threatening to unleash,” said Lytle Hernández, who holds the Thomas E. Lifka endowed chair of history at UCLA. “It is not just mass deportation; it’s mass racial banishment.”

Even if the program doesn’t come to pass, promoting such a plan only deepens the marginalization of Latino and immigrant communities in the United States, Lytle Hernández added.

That was an issue in the 1950s, too, when newspapers were splashed with headlines about the “surge in border crossings.” In 1954, the New York Times described immigrants continuing to “invade the U.S. in an unending - and uncontrolled - stream.” “Two Every Minute Across the Border,” the headline read.

That same year, Sen. Carl Hayden, D-Ariz., sent a letter to President Dwight D. Eisenhower blaming American unemployment on the “influx of Wetbacks out of Mexico and aliens from other countries who are here illegally.”

Immigration from Mexico increased in the 1940s with the establishment of the “bracero program,” an agreement between the United States and Mexico that recruited millions of Mexican men to legally work on short-term labor contracts - a deal aimed at addressing a national agricultural labor shortage during World War II.

But the program excluded women and children, Lytle Hernández said, driving some families to enter the country illegally to remain together. And growers along the border states often preferred hiring undocumented migrants whom they paid lower wages, she added.

Worried about losing too many of its workers, the Mexican Embassy warned the U.S. State Department that if control was not established, the bracero agreements would be overhauled, Lytle Hernández wrote in a 2006 article about the Eisenhower-era deportation operation. As a result, the article states, the United States began ramping up deportations - and setting off a decade-long campaign that climaxed in the summer of 1954.

In June 1954, the head of the U.S. Border Patrol vowed to set forth “the biggest drive against illegal aliens in history,” the Los Angeles Times reported at the time. Under Swing, then the commissioner of the INS, the campaign started in California and quickly stretched to Arizona, Texas and Illinois.

Hundreds of agents were deployed to locate and deport anyone suspected of being in the United States illegally - sometimes mistakenly targeting American citizens, according to historians. People were transported into Mexico “like cows” in trucks or on boats that a congressional investigation likened to an “eighteenth century slave ship,” Columbia University historian Mae Ngai detailed in “Impossible Subjects.”

According to Ngai, 88 people died of heatstroke in Mexicali after they were rounded up in blistering 112-degree heat. In another incident, a riot broke out on an overpacked ship in the Gulf of Mexico, prompting 37 people to jump into the water. Five of them drowned, Ngai wrote.

Chicago-based attorney Joaquín “Jack” Sanchez, 40, said the operation had a lasting effect on his family. In 1954, agents arrived at his grandmother’s home in La Feria, Texas, where she settled with her husband and six children, who were all American citizens.

Sanchez’s grandmother, Aurora, was excluded from immigrant work programs because of her gender. Her husband worked in agriculture and Aurora sold food to the workers and took care of children, Sanchez said. But that summer, she was given just minutes to pack up her life before agents took her to a detention center, he said.

Aurora, with a “stern face and piercing green eyes,” Sanchez said, recalls explaining she had six U.S.-born children, including an infant. Officials told her to bring the child - Sanchez’s mom, Noelia - with her.

Noelia and her mother were taken across the border and left in Reynosa, about 130 miles northwest of Monterrey, where Aurora’s family lived. “She was fortunate to have, I believe, one of her brothers or an uncle pick her up,” Sanchez said.

Two years passed before Aurora and Noelia were able to reunite with the rest of their family in Chicago, where they still live. The traumatic deportation has affected the family for generations, Sanchez said, leaving them feeling conflicted toward the U.S. government. “We’re constantly put in this place of being incarcerated or policed or monitored,” he said.

The point of the military-style “publicity campaign” in the 1950s was to conduct mass deportations quickly and on an impressive scale, Lytle Hernández said. Officials wanted to address Americans’ growing concerns about a border crisis and generate enough fear over deportations to push returning or deported migrants into joining the bracero program. Those goals could only be accomplished if there was media coverage, she added, so officials invited reporters to observe the operation and sent news releases to towns ahead of raids.

Decades later, the deportation campaign is now decried as a “shameful time in American history,” as 21 members of Congress put it in a recent letter to Attorney General Merrick Garland. In 2020, the Los Angeles Times apologized for acting as “an uncritical mouthpiece for Washington as it covered the Eisenhower administration’s” operation.

And though since 2015 Trump has flouted the operation as a “very effective chapter” in American history - and one in which brutal tactics resulted in migrants “never [coming] back” - its success was deeply exaggerated, historians say.

Although officials claimed the summer operation led to 1.3 million apprehensions, scholars including Lytle Hernández have challenged that figure - saying that those statistics include arrests from previous years. According to Lytle Hernández, the number of apprehensions for fiscal year 1955 was about 250,000.

In 1955, the Congressional Committee on Appropriations also questioned the INS’s claims that the operation had led to 540,000 deportations in California - especially because records pointed to about 84,000 apprehensions during that period.

The operation, however, led to another unexpected outcome, Lytle Hernández said: It helped increase the number of braceros by encouraging immigrants who had been working in the United States illegally to become legal.

But ultimately, it cultivated fear, Lytle Hernández said, adding that Trump’s proposal would repeat a dark chapter of history.

“With him making these threats, the campaign has already begun,” she said. “The dimension of it that’s about racial terror is already afoot.”