Before being confirmed as the director of the FBI, Kash Patel made clear his intent to remake it in his own image, reflecting a larger desire by the White House to bend the agency to its will.

"The FBI has become so thoroughly compromised that it will remain a threat to the people unless drastic measures are taken," he wrote in his book Government Gangsters, asserting that the top ranks of the bureau should be eliminated.

Behind the scenes, his vision of an FBI under President Trump is quietly taking shape. Agents have been forced out. Others have been demoted or put on leave with no explanation. And in an effort to hunt down the sources of news leaks, Patel is forcing employees to take polygraph tests.

Taken together, the moves are causing worrisome upheaval at the FBI, eliciting fear and uncertainty as Patel and his deputy, Dan Bongino, quickly restock senior ranks with agents and turn the agency's attention to immigration. Their persistent claims that the bureau was politicised under previous directors, in addition to their swift actions against colleagues, have left employees to wonder whether they, too, will be ousted, either because they worked on an investigation vilified by Trump supporters or had ties to the previous administration.

The actions have obliterated decades of experience in national security and criminal matters at the FBI and raised questions about whether the agents taking over such critical posts have the institutional knowledge to pursue the cornerstones of its work.

"The director and I will have most of our incoming reform teams in place by next week," Bongino wrote on social media last week. "The hiring process can take a little bit of time, but we are approaching that finish line. This will help us both in doubling down on our reform agenda."

He added that the agency would revisit past investigations, like the 2022 leak of a draft Supreme Court opinion on abortion, cocaine found two years ago at the White House and the pipe bombs found near the Capitol on January 6, 2021.

Former and current FBI officials warned that the attempts by Trump loyalists to mould the bureau to their worldview could ultimately have a chilling effect on agents seeking to open cases that could upset Trump or his base. They added that they viewed many of the personnel moves as retribution.