The U.S. House of Representatives then appointed the "Lampert Committee" in October 1924 to investigate Patrick's criticisms. Mitchell testified before the committee and, upset by the failure of the War Department to even negotiate with the Navy in order to save the reforms of the Lassiter Board, harshly criticized Army leadership and attacked other witnesses. He had already antagonized the flag and general officers of both services with speeches and articles delivered in 1923 and 1924, and the Army refused to retain him as Assistant Chief of the Air Service when his term expired in March 1925. He was reduced in rank to colonel by Secretary Weeks and exiled to the Eighth Corps Area in San Antonio as air officer, where his continuing, reckless, and increasingly strident criticisms prompted President Calvin Coolidge to order his court-martial. Mitchell's conviction on December 17, 1925, followed by three days the Lampert Committee's recommendations for creation of a unified air force independent of the Army and Navy; creation of "assistant secretaries for air" in the War, Navy, and Commerce Departments; and establishment of a Department of National Defense.