Lt. Col. Alexander Vindman, a key witness in President Donald Trump’s impeachment inquiry, is retiring from the US Army after more than 21 years of military service because he determined that his future in the armed forces “will forever be limited” due to political retaliation by the President and his allies, his lawyer told CNN Wednesday. Vindman has endured a “campaign of bullying, intimidation, and retaliation” spearheaded by the President following his testimony in the impeachment inquiry last year, according to his attorney, Amb. David Pressman who is a partner at Jenner & Block. News of Vindman’s retirement marks the culmination of a months-long saga dating back to his public testimony in November. Trump fired Vindman as the top Ukraine expert on the National Security Council in February and also ousted his twin brother who also played a key role in impeachment proceedings while serving at the White House as an NSC lawyer. In recent weeks, the controversy has centered around allegations that the White House was attempting to block Vindman’s upcoming military promotion to the rank of colonel. “The President of the United States attempted to force LTC Vindman to choose: Between adhering to the law or pleasing a President. Between honoring his oath or protecting his career. Between protecting his promotion or the promotion of his fellow soldiers,” Pressman said in a statement to CNN. “These are choices that no one in the United States should confront, especially one who has dedicated his life to serving it,” he added, noting that Vindman “did what the law compelled him to do; and for that he was bullied by the President and his proxies.” Top Pentagon leaders, including Secretary of Defense Mark Esper, have insisted that Vindman is not being targeted for political reasons, but a source familiar with his decision said military officials have communicated to Vindman that the White House has sought to become involved in the promotion process. In response, Vindman was told that that there have been discussions within the Department of Defense about sending his name forward on a “list of one” or holding his name back until after the election to avoid impacting the promotions of other service members, the source said. It is “absurd and frightening” for the White House to be involved in promotions at this level, the source added. Ultimately, Vindman decided to retire from the military rather than attending the National War College, which was his next planned assignment, after speaking with senior Army officials who made clear that there were forces working against his advancement within the military. Specifically, Vindman was told by senior Army officials that he would no longer be deployable in his area of expertise, which includes Ukraine, the source familiar with the situation told CNN. He was also told by senior officers he would need a “rehabilitative assignment” even if he had opted to attend the National War College, an option he had been considering before Wednesday’s announcement, the source added. In one case, a senior officer quipped about sending him to “man a radar station in Alaska,” the source said. The White House did not immediately respond to CNN’s request for comment. Despite the extensive delays and reports of White House pressure, a defense official told CNN that Vindman’s nomination for a promotion proceeded with no flags from the Pentagon. “This was all handled in a normal process,” the official said. The official also said that Esper had already approved the list of promotions put forward by the Army, including Vindman’s promotion to colonel, and that list was still scheduled to go to the White House on Wednesday. Impeachment retaliation Vindman delivered explosive testimony during public impeachment hearings that Trump’s push for Ukraine to investigate former Vice President Joe Biden was “inappropriate” and that he knew “without hesitation” that he had to report it. Vindman said that he reported his concerns out of a “sense of duty,” and he defended his fellow witnesses from what he described as “reprehensible” attacks. Testifying in his Army uniform as an active-duty soldier, Vindman invoked his father’s decision to leave the Soviet Union and come to the US, noting that the testimony he was giving would likely get him killed in Russia. “Do not worry, I will be fine for telling the truth,” Vindman said in a now well-known line. But Vindman remained a focal point of Trump’s ire as impeachment proceedings moved to the Senate, facing a wave of unfounded attacks from the President and his allies during the trial portion. During oral arguments in the Senate trial in late January, Sen. Marsha Blackburn, a Tennessee Republican, attacked Vindman in multiple tweets over several hours, going so far as to question the Purple Heart recipient’s patriotism. She also repeated the unfounded claim that Vindman had leaked knowledge of Trump’s July 25 phone call with Ukrainian President Volodymyr Zelensky to the whistleblower whose complaint initially prompted the investigation into the President’s conduct in Ukraine. After he was fired from the NSC in February, an Army spokesperson told CNN that Vindman had been reassigned to the Department of the Army. The President later defended Vindman’s firing from the National Security Council. Trump complained about news coverage of the firing in a tweet, saying reporting was done “as though I should think only how wonderful he was. Actually, I don’t know him, never spoke to him, or met him (I don’t believe!).” Democrats called on Esper to protect Vindman Top military leaders, including Esper, have insisted that Vindman would be protected from retaliation of any kind after he transitioned back to the Pentagon, but some Democratic lawmakers have made it clear they believe that he is still being targeted by the White House. Democratic Sen. Tammy Duckworth of Illinois announced last week that she is blocking Senate confirmation of 1,123 senior US Armed Forces promotions until she receives assurances that Vindman’s promotion wouldn’t be blocked. The initial list of promotions Duckworth is holding up does not include Vindman’s name, as he is included in a later batch. Duckworth’s power play, which her office described as “unprecedented in modern history,” takes advantage of unanimous consent procedures in the Senate that are used to efficiently conduct Senate business. Typically, a large batch of non-controversial military promotions, like the ones Duckworth is holding up, would be passed all at once with just a few words exchanged on the floor between Majority Leader Mitch McConnell and whoever is the presiding officer. But instead of granting consent to pass the promotions, Duckworth objected, meaning McConnell would have to go through the time-consuming process of filing motions to overcome what amounts to her filibuster. Duckworth said in a statement Wednesday that Vindman’s decision to retire “puts the spotlight on Secretary of Defense Mark Esper’s failure to protect a decorated combat Veteran against a vindictive Commander in Chief” and that her partial hold on military promotions will remain in place until he “provides a transparent accounting of this disgraceful situation.” “Secretary Esper’s failure to protect his troops sets a new, dark precedent that any Commander in Chief can interfere with routine merit-based military promotions to carry out personal vendettas and retaliation against military officers who follow duly-authorized subpoenas while upholding their oath of office and core principles of service,” Duckworth wrote. In an interview with CNN last week, Trump’s former national security adviser John Bolton said he believed Vindman, who worked under him at the NSC, deserved to be promoted based on what he observed during his time in the administration. “Based on not just his service, but his twin brother’s service at the NSC, both of whom were pushed out of their assignments early, I think they certainly deserve promotion based on what I saw,” Bolton said to CNN’s Jake Tapper while promoting his new book “In the Room Where it Happened.” “They shouldn’t be discriminated against. I hope there’s nobody in the White House who’s holding this up or putting bureaucratic obstacles in the way,” he added. “I think this is something, this kind of corruption of this promotion process, unfortunately, typical of a number of things that have happened in the administration, I think it’s a bad signal to all of our military.” This story has been updated with reaction to Vindman’s decision.