Introduction: The Power of Lineage

Pedro Mexía began his 1548 biography of Charles V with a telling phrase: “Let us begin with his lineage.” The opening chapter, titled “The Illustrious, Excellent, and Undoubted Genealogy and Descent of This Great Monarch,” traced the emperor’s ancestry back through a thousand years of European rulers. Mexía correctly identified Charles’s most valuable asset—his family connections—though modern historians might view his account as somewhat exaggerated. When Charles was born in 1500, his father, Archduke Philip of Austria, ruled only the Netherlands provinces inherited from his mother, Mary of Burgundy. Yet Philip stood to inherit the distant Central European territories of his father, Maximilian, head of the House of Habsburg. Charles’s mother, Joanna, initially had little prospect of inheriting substantial lands, being the third child of Isabella of Castile and Ferdinand of Aragon, the “Catholic Monarchs” of Spain. This seemingly modest inheritance would, through a remarkable convergence of dynastic accidents and strategic marriages, create history’s first global empire.

The Three Dynasties: Trastámara, Burgundy, and Habsburg

The Trastámara, Burgundian, and Habsburg dynasties shared several crucial characteristics that would enable their eventual unification under Charles V. Most importantly, all three houses practiced imperial expansion through strategic marriage alliances rather than purely through military conquest.

The Trastámara family had pursued intermarriage between its Castilian and Aragonese branches for generations, hoping to unify these Iberian kingdoms. They also married into Portugal’s Aviz dynasty, aspiring to unite the entire Iberian Peninsula under their rule. The dukes of Burgundy had followed a similar strategy from their dynasty’s inception—the first duke married the heiress of Flanders in 1369, then acquired most other Netherlandish territories through inheritance. The Habsburgs used marriage both to acquire new territories and to strengthen bonds between family branches, leading to the popular motto that emerged after Maximilian of Austria married Mary of Burgundy in 1477: “Let others wage war; you, happy Austria, marry! What Mars gives to others, Venus gives to you.”

This marital imperialism came with significant costs. The resulting political entities stood in stark contrast to modern nation-states: loyalty to the dynasty often provided the only common bond between territories, encouraging rulers to view their disparate domains—however geographically separated—as personal property to be preserved intact for the next generation. In 1543, Charles V assured his son, the future Philip II, that his primary goal was “to prevent you from inheriting less than I received.”

The French Threat: A Unifying Fear

Fear of France provided another common thread binding these three dynasties. Burgundy had signed anti-French treaties with Aragon as early as the 1470s; a decade later, Maximilian proposed marrying his only son to a Spanish princess, though negotiations progressed slowly. The situation changed dramatically in 1494 when King Charles VIII of France invaded Italy and marched triumphantly into Naples to claim its throne. The following year, Maximilian warned Spain’s Catholic Monarchs: “Once the French king gains Naples, he will covet the other states of Italy.” To persuade them to “resist and attack the French king,” Maximilian proposed a double marriage alliance: his daughter Margaret would marry the Spanish heir, Prince John, while his own heir, Philip, would wed the Catholic Monarchs’ youngest daughter, Joanna.

The marriage agreements were signed in January 1495, and the Spanish princess arrived near Antwerp in October 1496 to marry Philip. Nobody could have predicted that the son of Philip and Joanna would eventually rule the largest empire the world had seen in a millennium.

The Conception and Birth of an Emperor

Charles V made his presence felt even before birth. In September 1499, Philip “commanded a midwife from the city of Lille” to “visit and attend to” Joanna; four months later, he dispatched a messenger “to proceed with all haste, day and night, sparing neither man nor horse” to borrow the most precious relic from a monastery near Lille—the “Virgin’s Ring.” According to tradition, this was the ring Joseph placed on Mary’s finger at their wedding, believed to “bring comfort to women in childbirth.”

Contemporary accounts suggest the ring worked miraculous effects. Joanna went into labor while attending a ball at the Palace of the Counts of Flanders in Ghent. She barely reached the nearest privy chamber before giving birth to the future emperor on February 24, 1500—the feast day of Saint Matthias. The city’s chief poet, an eyewitness to the events, recorded the birth with appropriate grandeur, recognizing the significance of this child who entered the world in such undignified circumstances but was destined for extraordinary power.

The Accidental Inheritance

Charles’s path to power resulted from a series of unexpected deaths that eliminated those ahead of him in the line of succession. His maternal grandparents, Ferdinand and Isabella, had five children: Isabella, John, Joanna, Maria, and Catherine. The eldest daughter, Isabella, married King Manuel I of Portugal but died in childbirth in 1498. Her son Miguel briefly became heir to both Portugal and Spain but died in infancy in 1500, the year Charles was born.

Prince John, the only male heir, married Margaret of Austria in 1497 but died just six months later without issue. This left Joanna as the heir to Castile and Aragon, though her mental instability would later become a significant political problem. Through these tragic circumstances, Charles became heir to the Spanish kingdoms despite being the third child of the third child of the Catholic Monarchs.

On his father’s side, Charles stood to inherit the Burgundian Netherlands and the Austrian Habsburg lands. When Philip the Handsome died unexpectedly in 1506, the six-year-old Charles inherited the Netherlands. His grandfather Ferdinand ruled Aragon until his death in 1516, while his other grandfather, Maximilian, held the Holy Roman Empire until 1519. Through this combination of strategic marriages and fortunate accidents of mortality, Charles inherited a collection of territories spanning Europe and eventually the Americas.

Governing a Disparate Empire

The empire Charles inherited presented extraordinary governance challenges. His territories included: the Netherlands, a wealthy commercial region with strong urban traditions; Spain, recently unified but with strong regional identities; Austrian hereditary lands in Central Europe; the Kingdom of Naples and Sicily in southern Italy; and rapidly expanding American colonies. Each territory had its own laws, customs, languages, and political institutions.

Charles struggled throughout his reign to manage these diverse domains. He faced major revolts in Spain , the Netherlands, and even among his German princes. His attempts to create centralized institutions often met with resistance from local elites protective of their privileges. The emperor spent much of his life traveling between his territories, attempting to personally administer his far-flung domains.

The Religious Challenge

Charles’s reign coincided with the Protestant Reformation, which began in 1517 when Martin Luther published his Ninety-five Theses. As Holy Roman Emperor, Charles faced the difficult task of maintaining religious unity while addressing legitimate criticisms of Church practices. He initially tried to find a middle ground, giving Luther a hearing at the Diet of Worms in 1521 but ultimately declaring him an outlaw.

The Reformation created particular problems in Charles’s German territories, where many princes adopted Protestantism partly as a means of asserting independence from imperial authority. This led to decades of religious conflict that culminated in the Schmalkaldic War of 1546-1547. Although Charles achieved military victory, he could not crush Protestantism, ultimately agreeing to the Peace of Augsburg in 1555, which established the principle of cuius regio, eius religio .

The Global Dimension

Charles’s inheritance included Spain’s burgeoning American empire. During his reign, Hernán Cortés conquered the Aztec Empire . These conquests brought enormous wealth to Spain in the form of silver and gold but also raised complex ethical and administrative questions.

Charles concerned himself with the treatment of indigenous Americans, convening debates at Valladolid about the nature and rights of native peoples. He promulgated the New Laws of 1542, which sought to protect indigenous populations from the worst abuses of the encomienda system, though enforcement proved difficult across the vast distances of the empire.

Abdication and Legacy

Exhausted by decades of travel, warfare, and administration, Charles began the process of dividing his empire in the 1550s. In 1555, he abdicated as ruler of the Netherlands; in 1556, he resigned his Spanish crowns and Italian territories to his son Philip II; and he finally resigned as Holy Roman Emperor in 1558 in favor of his brother Ferdinand.

He retired to the Monastery of Yuste in Extremadura, Spain, where he died in 1558. His empire was divided between the Spanish and Austrian branches of the Habsburg family, creating the Spanish Habsburgs who would rule Spain and its global empire, and the Austrian Habsburgs who would continue to rule the Holy Roman Empire and Central European territories.

Charles’s reign marked a transition between medieval and modern Europe. His empire was the last great political entity organized primarily around dynastic rather than national principles. Though he struggled to maintain unity across his diverse territories, his reign saw the first attempts to create administrative structures for a global empire. The marriage policies that created his inheritance ultimately proved unsustainable, but they produced one of history’s most remarkable political formations—an empire on which the sun never set.

Conclusion: The Marital Empire

The story of Charles V’s inheritance demonstrates the power and limitations of dynastic marriage as a tool of empire-building. The careful marital strategies of the Trastámara, Burgundian, and Habsburg houses created unprecedented territorial accumulations, but they also produced a polity so diverse and dispersed that it defied coherent governance. Charles’s life became an endless journey between his territories, attempting to personally embody the only thing that united them: his own person as the inheritor of these carefully arranged marriages.

The empire built through weddings rather than conquests prefigured modern globalization in some ways while remaining thoroughly medieval in its personalistic conception of power. Charles’s eventual decision to divide his inheritance acknowledged that such vast territories could not be effectively governed as a single unit. Yet for several decades, this accidental emperor ruled the most extensive collection of territories in a thousand years, all thanks to the marital calculations of his ancestors and the unpredictable hand of fate that made him the beneficiary of these arrangements. The empire of Charles V stands as a testament to both the possibilities and limitations of power built through strategic marriages rather than national consolidation.