Lt. Col. Alexander Vindman, a key witness in President Donald Trump’s impeachment inquiry, retired from the U.S. Army after more than 21 years of military service. According to Vindman’s attorney, David Pressmen, his client determined that his future in the armed forces “will forever be limited” due to political retaliation by the President and his allies. Vindman has endured a “campaign of bullying, intimidation and retaliation” spearheaded by the President following his testimony in the impeachment inquiry last year, Pressman said.

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 on allegations that the White House was attempting to block Vindman’s upcoming military promotion to the rank of colonel.