When President Trump vowed to deport “millions” of immigrants from the United States, he was telegraphing an Immigration and Customs Enforcement operation that targeted migrants with final deportation orders. The real list had about 2,100 families on it, with the goal of deterring Central American migrants from trying to cross the southern border.

The final tally from the operation, according to federal officials: Eighteen family members were arrested, not enough to fill a school bus. Immigration officials arrested another 17 undocumented immigrants they encountered in their searches, what are known as collateral arrests.

ICE announced the data Tuesday morning, tucking it into a news conference that included information about worksite enforcement and routine criminal arrests. Aside from the 35 immigrants apprehended in the much-anticipated family operation, immigration agents separately picked up nearly 900 adults — most of them convicted criminals — and delivered more than 3,000 notices to companies nationwide that authorities will audit their records to ensure that workers are in the United States legally.

Acting ICE Director Matthew T. Albence called the criminal operation successful and said the family operation, Operation Border Resolve, will continue, although the number of arrests were lower than in the past. The first such operation, over New Year’s weekend in 2016 under the Obama administration, led to the arrests of 121 adults and children in Georgia, Texas and North Carolina.

Officials would not say where the arrests were made during the recent operation nor when the operation took place, and immigration arrests are not public record. Families were not separated during the arrests, Albence said.

Albence said public blowback and publicity surrounding the raids probably dampened their numbers, but he said that the operation was “just the beginning” and that immigration agents would continue to pursue family members with deportation orders.

On June 22, President Trump spoke to reporters about an expected U.S. Immigration and Customs Enforcement roundup of migrant families with deportation orders. (The Washington Post)

“We’re patient, and we’ll continue to pursue these cases,” Albence said. “They may have escaped detection for a short period of time, but we’re going to continue to be out there working these cases.”

As Immigration and Customs Enforcement plans to round up migrants with deportation orders, an immigration debate ignited on July 14. (Monica Akhtar/The Washington Post)

ICE’s arrest numbers illustrate the vast distance between the president’s ambitions for mass removals of immigrants from the country and the on-the-ground challenges facing an agency that has been struggling with limited resources and a record influx of Central American families at the U.S.-Mexico border.

Immigration arrests from the interior have been flat for months as Democratic mayors, members of Congress, church pastors and local residents rally to shield immigrants from deportation, such as one episode Monday in a Nashville neighborhood that thwarted at least one arrest. Federal immigration agents have long said they focus on arresting people who commit crimes and on recent border crossers, but they have struggled to detain and deport them.

Trump has threatened the mass arrests since June 17, but he called them off five days later. The president tweeted that he delayed the raids for two weeks at Democrats’ request, “to see if the Democrats and Republicans can get together and work out a solution to the Asylum and Loophole problems at the Southern Border.”

“If not,” he wrote, “Deportations start!”

Trump and his officials continued to publicize the raids, and the president said this month that the sweeps would start July 14. Albence did not fault the president for telegraphing the raids, but federal law enforcement operations generally are not publicized ahead of time to protect officers’ safety and avoid tipping off their targets before they are caught.

Albence said that the migrant families had been given a chance to file asylum claims and that most did not show up for their court hearings, a sign he said points to the cases being fraudulent and an indication that the migrants were coming to the United States for work, not to escape persecution. He said just 65 of the 2,100 families who were notified of their removal orders accepted the agency’s invitation to leave the United States voluntarily.

The Department of Homeland Security and the Justice Department drafted plans for the “family operation” in late 2018 to expel some of the hundreds of thousands of Central American parents and children who have been arriving during the past year. Officials claimed 90 percent of those who were ordered to be deported did not show up for their immigration court hearings.

ICE’s initial target list focused on as many as 10 U.S. cities that are major destinations for immigrants, including Houston, Los Angeles and New York.

Top White House officials urged going forward with the operation, largely as a show of force, hoping that it would deter potential migrants from coming north toward the United States. Ken Cuccinelli II, acting director of U.S. Citizenship and Immigration Services, told Fox Business Network this month that ICE was “ready and raring to go.”

But internally, ICE officials expected to detain just 10 percent to 20 percent of their targets in each city, far fewer than the millions the president had pledged. Officials also have worried about intensifying public criticism of ICE.

A day before the most recent arrests were set to begin, a man arrived at an ICE detention center in Tacoma, Wash., with a rifle and incendiary devices. Officers fatally shot him.

Several nonprofit organizations filed a federal lawsuit to block the raids. Critics have said the Trump administration is targeting families, including small children, who fled poverty, hunger and violence in their homelands. Advocates for immigrants say most families are eager to attend their court hearings but that dates often are incorrectly scheduled or that migrants don’t receive the information about their hearings.

The White House says the influx of families is a smuggler-driven enterprise to sneak migrants into the United States to work, taking advantage of loopholes in federal law that require children to be released from custody soon after their apprehension at the border. Federal officials say adults are bringing children because they are likely to be released.