The Holy Roman emperor Charles V (1500-1558) inherited the thrones of the Netherlands, Spain, and the Hapsburg possessions but failed in his attempt to bring all of Europe under his imperial rule.

Born in Ghent on Feb. 24, 1500, Charles V was the oldest son of Philip the Fair of Hapsburg, Lord of the Netherlands, and Joanna the Mad of Aragon and Castile. When Philip died in 1506, Charles was in line for the rich inheritance of the Netherlands as well as Hapsburg Austria and possibly the office of emperor. Spain--the product of the rather recent union of Aragon and Castile under the Catholic Kings--fell to him because of a series of deaths in the Spanish family, which made his mother, Joanna, the legal successor to the Spanish throne.

Charles's maternal grandfather, Ferdinand of Aragon, who had long tried to block a Spanish-Hapsburg union, favored the succession of Charles's younger brother...