President-elect Donald Trump has made the securing of our southern border and the expulsion of undocumented immigrants from our country the foundation of his inaugural policies. In his first 100 days in office, he plans to launch the largest expulsion of undocumented immigrants in our nation’s history—between 2 and 3 million immigrants.

Expelling this many people may sound logistically impossible, but efforts on this scale have been undertaken before, as Trump well knows. During the Republican primary debates, he referred to President Eisenhower’s Operation Wetback, which deported an estimated 1.1 million undocumented migrants in 1954: “ ‘I like Ike,’ right? The expression. ‘I like Ike.’ Moved a million-and-a-half illegal immigrants out of this country, moved them just beyond the border. They came back. Moved them again beyond the border, they came back. Didn’t like it. Moved them way south. They never came back.”

This casual description of the program belies a misunderstanding of what it actually accomplished—and why we would never want it to happen again. Operation Wetback was not simply the enforcement of immigration laws but a campaign of fear against immigrants. Its goal was to draw lines between who was and who was not American.

Operation Wetback was launched just as the racial underpinnings of our immigration policies began to be removed. Two years earlier, in 1952, our immigration laws had been changed so that, for the first time since our nation’s founding, being white was not a legal prerequisite for naturalization. Operation Wetback’s enforcement approach—assuming those who were not white had dubious citizenship—reflected the Immigration and Naturalization Service’s (and many American’s) resistance to this legal shift.

In 1953, INS commissioner Argyle Mackey complained of “the human tide of ‘wetbacks’ ” as the “most serious enforcement problem of the Service.” The first Mexican guest workers had come to the fields legally through the World War II braceros program, a series of laws and diplomatic agreements that allowed Mexicans to work on American farms. Mackey wrote, in the official INS house organ, that the reports of good work in the States to “the Mexicans left at home … turned the trickle into the flood” and for “every agricultural laborer admitted legally, four aliens were apprehended.” Willard Kelly, the assistant commissioner of the border patrol, called this “the greatest peacetime invasion ever complacently suffered by any country.” These concerns led the INS to launch, in 1954, what was officially called the “Special Mobile Force Operation,” or as it was actually referred to in the INS and in the American media, “Operation Wetback.” ...