Westmoreland served as Chief of Staff of the United States Army from 1968 to 1972. In 1970, as Chief of Staff, in response to the My Lai Massacre by United States Army forces (and subsequent cover up by the Army chain of command), he commissioned an army investigation that compiled a comprehensive and seminal study of leadership within the army during the Vietnam War demonstrating a severe erosion of adherence to the army's officer code of "Duty, Honor, Country". The report, entitled "Study on Military Professionalism", had a profound influence on Army policies, beginning with Westmoreland's decision to end the policy that officers serving in Vietnam would be rotated into a different post after only six months. However, to lessen the impact of this damaging report, Westmoreland ordered that the document be kept on "close hold" across the entire Army for a period of two years and not disseminated to War College attendees. The report became known to the public only after Westmoreland retired in 1972.