The sheer scale of the empire proved ungovernable for one person, leading to a permanent split in 1556 between the and the Austrian Habsburgs . The Rise and Fall of the Habsburg Empire
Under Charles V (r. 1519–1556), the empire reached its greatest territorial extent, functioning as the primary defender of Catholicism against the Ottoman Empire and the burgeoning Protestant Reformation. The Long Pivot: Division and Absolutism History of the Habsburg Empire: Rise and Declin...
Their son, Charles V , inherited a staggering dominion including Spain, the Americas, Austria, and the Netherlands. The sheer scale of the empire proved ungovernable