Ultimately, amid withering pressure, Trump provided the whistleblower complaint to Congress, as well as a transcript of a July 2019 call with Ukraine's president, two pieces of evidence that became crucial factors in the House's decision to impeach Trump for abuse of power. The Senate later acquitted him on a nearly party-line vote.

"As an Inspector General, I was legally obligated to ensure that whistleblowers had an effective and authorized means to disclose urgent matters involving classified information to the congressional intelligence committees, and that when they did blow the whistle in an authorized manner, their identities would be protected as a guard against reprisals," Atkinson said in his statement. "Inspectors General are able to fulfill their critical watchdog functions because, by law, they are supposed to be independent of both the Executive agencies they oversee and of Congress."

Trump informed the House and Senate Intelligence Committees late Friday that he would be removing Atkinson after a required 30-day wait. But Atkinson was immediately placed on administrative leave, according to congressional sources, effectively circumventing the one-month delay. The move has prompted some Senate Republicans to demand more details about Atkinson's removal.

Trump indicated in his letters that he had lost confidence in Atkinson but didn't explain why. When asked about the matter at a Saturday press conference, though, Trump cited Atkinson's handling of the whistleblower complaint. Though Trump has repeatedly assailed the complaint as false, many of the underlying details were corroborated by a string of State Department and White Hopuse witnesses during impeachment hearings.

“I thought he did a terrible job. Absolutely terrible,” Trump said of Atkinson on Saturday at a press conference, adding, “He took this terrible, inaccurate whistleblower report and he brought it to Congress."

Atkinson's ouster occurred as Trump moved to remake the ranks of inspectors general, naming a handful to vacant posts late Friday. He also nominated a White House attorney, Brian Miller, to the newly created post of special inspector general for pandemic recovery. The position, created as part of the $2 trillion coronavirus relief law signed late last month, is meant to oversee a $500 billion fund in the Treasury Department meant to stabilize the economy. Though Miller, a former federal inspector general, won plaudits from some transparency advocates, the pick drew quick criticism from House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer, who questioned whether a White House attorney could demonstrate independence from the president.

Trump's removal of Atkinson also drew a quick brushback from the Justice Department's current inspector general, Michael Horowitz, who heads a council of fellow IGs. Horowitz emphasized that Atkinson was widely respected in the IG community and was seen as having handled the Ukraine whistleblower complaint "by the book."

Atkinson, who remained silent through the impeachment process despite attacks from Trump allies in Congress, defended his handling of the whistleblower complaint.

"Those of us who vowed to protect a whistleblower’s right to safely be heard must, to the end, do what we promised to do, no matter how difficult and no matter the personal consequences," he wrote. "I will be forever grateful to the many public officials and others who fight tirelessly and consistently, in words and deeds, in ordinary and extraordinary matters, to protect the rights of all whistleblowers and, in turn, the best interests of the United States."

