Under Secretary of Defense for Policy John Rood, speaks during a news conference on the 2018 Nuclear Posture Review, at the…
FILE - Under Secretary of Defense for Policy John Rood speaks during a news conference at the Pentagon, Feb. 2, 2018.

U.S. President Donald Trump fired the Pentagon's top policy official Wednesday, the latest senior member of the administration to lose his job apparently because of Trump's lingering anger over impeachment and Ukraine.

Under Secretary of Defense for Policy, John Rood certified last year that Ukraine had made enough progress in fighting corruption to release nearly $400 million in U.S. military aid — four months before the money was actually released.

Rood made no mention of Ukraine in his resignation letter to Trump, only saying he understands from the defense secretary that Trump asked him to leave.

President Donald Trump greets supporters after arriving at Palm Springs International Airport in Palm Springs, Calif., en route to a fundraiser in Rancho Mirage, Calif., Feb. 19, 2020, in Palm Springs, Calif.

A Pentagon spokesman only said "The president has the opportunity and the ability to have the team that he wants to have in policy positions" and “can make a decision to go in a different direction.”   

After Congress approved nearly $400 million in badly-needed military aid to Ukraine, Rood certified in May 2019 that Ukraine "has taken substantial actions to make defense and institutional reforms for the purpose of deceasing corruption." Such certification was needed before the money could be released.

But Rood's certification undermined the White House's insistence that corruption in Ukraine was an ongoing concern as a reason to continue to withhold the funds.

The White House kept insisting this was the reason even while top U.S. diplomats started to realize that the president wanted Ukraine to investigate Democratic presidential candidate Joe Biden in exchange for the aid.

Rood told reporters last year that "In the weeks after signing the certification, I did become aware that the aid had been held. I never received a very clear explanation other than there were concerns about corruption in Ukraine."

Rood said at the time he was concerned that sitting on the money would hurt U.S. security.

Trump's infamous July 25 telephone call in which he asked Ukrainian President Volodomyr Zelenskiy for a "favor" led to his impeachment.

House Democrats said the only reason Trump eventually released the money for Ukraine was because he was "caught" when an intelligence whistleblower expressed concerns about the call.

Rood is the latest high-profile administration official forced to resign in the wake of impeachment and Trump's Senate acquittal.

FILE - Lt. Col. Alexander Vindman, left, walks with his twin brother, Yevgeny Vindman, after testifying before the House Intelligence Committee, on Capitol Hill in Washington, Nov. 19, 2019.

Lt. Col. Alexander Vindman, the top European expert on the National Security Council whose testimony bolstered the case against Trump, has been reassigned.

His twin brother, Yevgeny Vindman, an NSC lawyer who was not part of the impeachment hearings, was dismissed for no clear reason.

Ambassador to the European Union Gordon Sondland, who was also a key witness in the impeachment probe, was recalled.