Emperor of Germany, son of Frederick III., acquired Burgundy and Flanders by marriage, which involved him in a war with France; became emperor on the death of his father in 1493; became by marriage Duke of Milan, and brought Spain under the power of his dynasty by the marriage of his son Philip to the daughter of Ferdinand and Isabella; it was he who assembled the Diet of Augsburg at which Luther made appeal to the Pope (1459-1519).