Stephen Miller and Thomas Homan had critical roles in the first Trump administration and are unapologetic defenders of its policies, which included separating thousands of parents from their children at the border to deter illegal crossings. With Trump promising sweeping action in a second term on illegal immigration, the two White House advisers will bring nuts-and-bolts knowledge, lessons from previous setbacks and personal views to help him carry out his wishes.

After Trump left office in 2021, Miller became president of America First Legal, a group that joined Republican state attorneys general to derail President Joe Biden’s border policies and plans. Homan, who worked decades in immigration enforcement, founded Border 911 Foundation Inc., a group that says it fights against “a border invasion” and held its inaugural gala in April at Trump’s Florida estate.

Homan “knows how the machine operates,” said Ronald Vitiello, a former Border Patrol chief and acting Immigration and Customs Enforcement director under Trump. “He did it as a front line, he did it as a supervisor, and he did it as the lead executive. He doesn’t have anything to learn on that side of the equation.”

Miller, he said, is deeply knowledgeable, has firm ideas about how the system should work, and has Trump’s confidence.

Trump has promised to stage the largest deportation operation in American history. There are an estimated 11 million people in the country illegally. Questions remain about how people in a mass raid would be identified and where they would be detained.

Miller and Homan portray illegal immigration as a black-and-white issue and applaud Trump’s policy of targeting everyone living in the country without status for deportation.

Trump frequently and sharply attacked illegal immigration during his campaign, linking a record spike in unauthorized border crossings to issues ranging from drug trafficking to high housing prices. The arrival of asylum-seekers and other migrants in cities and communities around the country has strained some budgets and broadly shifted political debate over immigration to the right, with Democratic nominee Kamala Harris during her campaign reversing several of her old positions questioning immigration enforcement.

Miller, 39, is a former Capitol Hill staffer who rose to prominence as a fiery Trump speechwriter and key architect of his immigration policies from 2017 to 2021. He has long espoused doomsday scenarios of how immigration threatens America, training his rhetoric on people in the country illegally but also advocating curbs on legal immigration.

Trump, Miller said at the former president’s Madison Square Garden rally last month, was fighting for “the right to live in a country where criminal gangs cannot just cross our border and rape and murder with impunity.”

“America is for Americans and Americans only,” he added.

Homan, 63, decided on a career in law enforcement as a boy in West Carthage, New York, watching his father work as a magistrate in the small farming town. After a year as a police officer in his hometown, he joined the Border Patrol in San Diego and remembers thinking, “What the hell did I just do?”

Homan, then working in relative obscurity as a top ICE official, said in a 2018 interview with The Associated Press that he got “a seat at the table” under President Barack Obama’s homeland security secretary, Jeh Johnson, to deliberate on policy change. Homan told others that he worried he may have been disrespectful and when word got back to the secretary, Johnson told him, “I may not agree with what you say, but I need to know what the effects are going to be if I don’t listen to you.”

Johnson said Monday that he didn’t recall the exchange but doesn’t dispute it, saying it sounded like him.

Homan rose to acting director of U.S. Immigration and Customs Enforcement under Trump. He was “significantly involved” in the separation of children from their parents after they crossed the border illegally and parents were criminally prosecuted, said Lee Gelernt, an attorney for the American Civil Liberties Union, which successfully sued to halt the practice.

Under a court settlement, families cannot be separated until December 2031 as part of a policy to deter illegal crossings. Trump has defended the practice, claiming without evidence last year that it “stopped people from coming by the hundreds of thousands.”

At the National Conservatism Conference in Washington earlier this year, Homan said while he thinks the government should prioritize national security threats, “no one’s off the table. If you’re here illegally, you better be looking over your shoulder.”

In the 2018 interview, Homan said he had no reservations about deporting a man who had been in the United States illegally for 12 years and with two children who are U.S. citizens. He likened it to a ticket for speeding motorists or an audit for a tax cheat.

“People think I enjoy this. I’m a father. People don’t think this bothers me. I feel bad about the plight of these people. Don’t get me wrong but I have a job to do,” he said.

He defended the “zero tolerance” policy that led to family separations when pressed by Democratic Rep. Alexandria Ocasio-Cortez in a congressional hearing. He likened it to arresting someone for driving under the influence with a young child as a passenger.

“When I was a police officer in New York and I arrested a father for domestic violence, I separated that father,” he said, inviting criticism that it was not the right analogy. Children couldn’t be quickly reunited with their parents at the border because government computers didn’t track that they were families. Many parents were deported while children were placed in shelters across the country.

Critics of zero tolerance have argued separations that happen during criminal cases involving American citizens are different from the separations under “zero tolerance,” when in many cases parents were deported without their children, who were sent to government-run facilities.

Miller and Homan do not require Senate approval, unlike homeland security secretary, ICE director and commissioner of U.S. Customs and Border Protection, which oversees the Border Patrol. Those appointees will be tasked with carrying out orders from the White House.