In a letter to Acting Inspector General Glenn Fine at the Defense Department, Schumer described the NSC firings as “part of a dangerous, growing pattern of retaliation against those who report wrongdoing only to find themselves targeted by the President and subject to his wrath and vindictiveness.”

In addition to asking Fine to investigate all acts of retaliation against those who reported presidential misconduct, Schumer also requested that the acting inspector general report the last time that personnel at the Defense Department were informed of their rights as whistleblowers. He also asked that Fine assure Congress in writing that the Pentagon’s general counsel would not allow retaliation against “anyone who has, or in the future makes, protected disclosures of presidential misconduct to Congress or Inspectors General.”

Alexander Vindman’s firing came two days after the Senate acquitted the president on charges of abuse of power and obstruction of Congress, after Trump withheld military aid to Ukraine and requested during a telephone call that the country’s president, Volodymyr Zelensky, investigate his political rivals.

Vindman, a Purple Heart recipient, told House investigators in October that Trump’s request undermined national security. He also considered the call with Zelensky inappropriate and flagged it for a top White House lawyer. Since his testimony, Vindman has come under repeated attacks from the president’s allies. Some Republicans, however, have come to his defense, citing his military service to the country.

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Trump also attacked Vindman on Saturday, saying he was “very insubordinate, reported contents of my ‘perfect’ calls incorrectly, & … was given a horrendous report by his superior, the man he reported to.”

David Pressman, one of Vindman’s lawyers, said the lieutenant colonel’s removal was nothing more than political retribution from the president.

Schumer wrote in his letter: “Without the courage of whistleblowers and the role of Inspectors General, the American people may never have known how the President abused his power in the Ukraine scandal. It is incumbent on you that whistleblowers … are protected for doing what we hope and expect those who serve our country will do when called: tell the truth.”