The Peace of Augsburg (1555) ended a struggle within the Holy Roman Empire between the Catholic Emperor Charles V and Lutheran princes. A key principle of the treaty was cuius regio, eius religio–“whose realm, his religion”–a prince could determine the religion of his state without interference from outside. It doesn’t seem like much, today; we wouldn’t say that freedom consists in believing as the prince directs you. But the principle acknowledged national, if not individual, autonomy in matters of religion, a major innovation at the time.

Last week, Yale University Press released a new biography of the Hapsburg prince and devoted Catholic who agreed to this arrangement, Emperor:A New Life of Charles V, by historian Geoffrey Parker (Ohio State). Here’s the description of the book from the Yale website:

Drawing on vital new evidence, a top historian dramatically reinterprets the ruler of the world’s first transatlantic empire.

The life of Emperor Charles V (1500–1558), ruler of Spain, Germany, the Netherlands, and much of Italy and Central and South America, has long intrigued biographers. But the elusive nature of the man (despite an abundance of documentation), his relentless travel and the control of his own image, together with the complexity of governing the world’s first transatlantic empire, complicate the task.
 
Geoffrey Parker, one of the world’s leading historians of early modern Europe, has examined the surviving written sources in Dutch, French, German, Italian, Latin, and Spanish, as well as visual and material evidence. He explores the crucial decisions that created and preserved this vast empire, analyzes Charles’s achievements within the context of both personal and structural factors, and scrutinizes the intimate details of the ruler’s life for clues to his character and inclinations. The result is a unique biography that interrogates every dimension of Charles’s reign and views the world through the emperor’s own eyes.