Matthew Albence, the top U.S. Immigration and Customs Enforcement official, announced his retirement in a statement Friday, leaving an agency at the forefront of President Trump’s immigration agenda without a clear successor.

Albence had directed ICE agents to back off some enforcement activity during the pandemic, frustrating some at the White House, but there was no indication that his decision to step down was intended as a statement of protest. His retirement from the job as deputy director and senior official performing the duties of director, had been rumored for months.

“After more than 25 years as a federal law enforcement officer, I am announcing my retirement from federal service,” Albence’s statement said. “This was an exceptionally hard decision to make, a decision prolonged due to the uncertainty of a global pandemic and the essential role ICE continues to play in our nation’s response. I am grateful for the opportunity to serve my country and to help protect it from those who would do it harm.”

Albence said he would work alongside Department of Homeland Security and ICE leadership “to ensure a smooth transition.”

Trump never formally nominated Albence for the top job at ICE, leaving him to serve in an acting role for more than a year. Well-liked by his workforce, Albence was known for his fierce defense of the agency and his unsentimental views on immigration enforcement. His comparison of ICE family detention facilities to “summer camp” during congressional testimony in 2018 was widely mocked, but it was reflective of his insistence that the agency has been unfairly stigmatized as cruel and harsh.

Albence’s retirement statement said as much. “Every day, against incredible odds, constant politicization, and misperceptions of the incredibly critical and complex mission they perform, ICE employees carry on with professionalism and integrity,” he said.

Trump, who took office vowing to immediately deport millions of immigrants, made ICE into a central element of his immigration agenda, and Albence welcomed the president’s praises. Behind the scenes, though, he sometimes pushed back on directives from the White House that he viewed as unworkable or unlawful, including a plan he resisted last year seeking to bus migrants to liberal-leaning “sanctuary cities.”

More recently, Albence clashed with Ken Cuccinelli, the acting deputy secretary of DHS, whom he viewed as attempting to interfere politically in his agency, according to DHS officials who described the tensions on the condition of anonymity because they were not authorized to discuss the situation publicly.

Albence leaves no clear successor, and several ICE officials contacted Friday said they were unsure who would take over. Derek Benner, who is the “senior official performing the duties of the deputy director,” is the top official in the agency’s investigative arm — Homeland Security Investigations — rather than Enforcement and Removal Operations, the division responsible for arrests, detention and deportations.

A documentary series featuring rare, up-close footage of ICE agents making arrests and describing the conflicting emotions of their work is scheduled to debut next week on Netflix, despite the agency’s objections. Albence is not among the ICE personnel who appear in trailers for the series “Immigration Nation,” which promises “unprecedented access to ICE operations.”