An American general of the Revolutionary War. He performed notably in the early days of the war but became bitter over several setbacks to his career. After receiving command of the American fort at West Point, New York, Arnold plotted to betray it to the British. The plan was revealed when the American forces captured Major John André of the British army, who was carrying messages between Arnold and the British. Arnold escaped to England and continued a military career, but he was widely scorned by the English.
Note: Calling someone a “Benedict Arnold” is to label the person a traitor.