Colonel William "Billy" Mitchell dropped out of college in 1898 to serve in the Spanish-American War. Afterwards, America stayed out of wars until 1917, when Mitchell was touring Europe as an observer. By then he was considered too old to be trained on the new airplanes that were just being considered, but he learned to fly through private lessons of his own. When the United States entered World War I, Mitchell was the first American to fly over enemy lines. In 1918, he led a large bombing attack on St. Mihiel.
After the war he devoted his efforts to advocating greater use of aviation in the military, and criticizing those who resisted the change. In 1921 and 1923 he bombed old American and captured German battleships to demonstrate how easily air power could sink them, which he did. The embarrassed military brass sent him on a trip to Asia, but when Mitchell returned he predicted that Japan would ultimately attack us as it did at Pearl Harbor.
In September 1925 a military airship crashed and killed many on board. Mitchell published a diatribe harshly criticizing his superiors, even accusing them of treason in ignoring the need for good military aviation. He was swiftly brought before a military court, known as a court-martial, for insubordination. He was tried for seven weeks.
Military courts lack the protections guaranteed to civilians in ordinary courts. The jury could not reach a unanimous verdict, which in a federal criminal case would prevent conviction. One juror, widely thought to be the future General Douglas MacArthur, voted for acquittal. But he was outvoted and Mitchell was convicted and sentenced to a humiliating loss of rank and pay. President Coolidge intervened to restore half his pay, but Mitchell quit the military instead.