Brigadier General William 'Billy' Mitchell (1879-1936), pilot and aviation and aerial bombing advocate, joined the army as a private and, by the Spanish-American War was the youngest lieutenant involved in the operation. Mitchell saw service in the Philippines, Cuba, and on the Mexican border, and graduated from the Army School of the Line (1908) and Army Staff College (1909) before serving on the Army General Staff (1913-1916). He held a number of command and staff posts in the Air Service in France during World War I (1917-1919) and first soloed in 1917. After a short period as Director of Military Aeronautics (1919) and Chief of Training and Operations (1920), he became Assistant to the Chief of Air Service (1921-1926). During this period he advocated the creation of an independent Air Service and demonstrated the utility of air power through the famous bomber vs. battleship trials (1921), the group flight to Alaska from the continental US (1923), and Army's Around the World Flight (1924). Unfortunately, Mitchell's public criticism of government policies, in defiance of Army regulations, resulted in his court martial for conduct prejudicial of 'good order and military discipline' and insubordination in October-December 1925. Found guilty and suspended for five years, Mitchell resigned his commission in January 1926. He continued to promote aviation and decry government inefficiencies until his death.