Updated at 6:49 p.m. ET
Lt. Col. Alexander Vindman, a key witness in the impeachment trial of President Trump, will retire Wednesday after 21 years in the military.
Vindman is leaving the Army "after it has been made clear that his future within the institution he has dutifully served will forever be limited," his lawyer, David Pressman, said in a statement. Recently, controversy has grown over an abnormal stall in his promotion to the rank of full colonel.