When Martin Luther issued grievances about the Catholic Church in 1517, King Henry VIII took it upon himself to personally repudiate the arguments of the Protestant Reformation leader. The pope rewarded Henry with the lofty title of Fidei Defensor, or Defender of the Faith.

Barely a decade later, the very same Henry VIII would break decisively with the Catholic Church, accept the role of Supreme Head of the Church of England and dissolve the nation’s monasteries, absorbing and redistributing their massive property as he saw fit.

So what changed? How did the former “Defender of the Faith” end up ushering in the English Reformation?

Though early signs of anticlericalism had surfaced in England by the 1520s, Catholicism still enjoyed widespread popular support. As for Henry VIII, he “had no wish and no need to break with the church,” says Andrew Pettegree, professor of history at the University of St. Andrews (U.K.). “No need because he already enjoyed substantial power over the English church and its income...And he had no wish also because he was personally rather pious.”

But by 1527, Henry had a big problem: His first marriage, to Catherine of Aragon, had failed to produce a son and male heir to the throne. Henry had also become infatuated with one of his wife’s ladies-in-waiting, Anne Boleyn, whose sister Mary had previously been his lover. Anne encouraged the king’s attention, but shrewdly refused to become his mistress, setting her sights on a higher goal.

So Henry asked Pope Clement VII to grant him a divorce from Catherine. He argued that the marriage was against God’s will, due to the fact that she had briefly been married to Henry’s late brother, Arthur.

Under other circumstances, it wouldn’t have been too difficult for England’s king to get a papal dispensation to set aside his first wife and marry another in order to produce a male heir. “There was a clear understanding among the princely houses of Europe that the continuation of the dynasty was the ruler's number one priority,” says Pettegree.

But the timing was not on Henry’s side. That same year—1527—the imperial troops of the Holy Roman Empire had attacked and destroyed Rome itself, forcing Pope Clement VII to flee the Vatican through a secret tunnel and take shelter in the Castel Sant’Angelo. At the time, the title of Holy Roman Emperor belonged to King Charles V of Spain—Catherine of Aragon’s beloved nephew.

With the papacy almost entirely under imperial sway, Clement VII was not inclined to grant Henry a divorce from the emperor’s aunt. But he didn’t want to completely deny Henry either, so he stretched out negotiations with the king’s minister, Cardinal Thomas Wolsey, over several years, even as Henry grew increasingly frustrated.

It was the clergyman Thomas Cranmer and the king’s influential adviser Thomas Cromwell—both Protestants—who built a convincing case that England’s king should not be subject to the pope’s jurisdiction. Eager to marry Anne, Henry appointed Cranmer as the Archbishop of Canterbury, after which Cranmer quickly granted Henry’s divorce from Catherine. In June 1533, the heavily pregnant Anne Boleyn was crowned queen of England in a lavish ceremony.

Parliament’s passage of the Act of Supremacy in 1534 solidified the break from the Catholic Church and made the king the Supreme Head of the Church of England. With Cranmer and Cromwell in positions of power, and a Protestant queen by Henry’s side, England began adopting “some of the lessons of the continental Reformation,” Pettegree says, including a translation of the Bible into English.

The Crown also moved to dissolve England’s monasteries and take control of the Church’s vast property holdings from 1536-40, in what Pettegree calls “the greatest redistribution of property in England since the Norman Conquest in 1066.” All of the property reverted to the Crown, and Henry used the windfall to reward his counselors, both Protestant and conservative, for their loyalty. “Even Catholics are extremely tempted by the opportunity to increase their landholdings with this former monastic property,” Pettegree says.

Anne Boleyn, of course, would fail to produce the desired son (although she gave birth to a daughter who would become Elizabeth I), and by 1536, Henry had fallen for another lady-in-waiting, Jane Seymour. That May, after her former ally Cromwell helped engineer her conviction of adultery, incest and conspiracy against the king, Anne was executed.

In October 1537, Jane Seymour gave birth to Henry’s first male heir, the future King Edward VI, before dying of complications from childbirth two weeks later. For the rest of Henry’s life, evangelical and conservative factions wrestled for influence—often with murderous results—but after Henry’s death in 1547, his son’s brief reign would be dominated by evangelical Protestant counselors, who were able to introduce a much more radical Reformation into England.

But Edward died young in 1553, and his Catholic half-sister, Queen Mary I, would reverse many of these changes during her reign. It would be left to Queen Elizabeth I, the daughter of Anne Boleyn and ruler of England for nearly 50 years, to complete the Reformation her father had begun.

“The divorce is absolutely at the heart of the matter,” Pettegree concludes. “Had there been no marital problems, I'm fairly certain there would have been no English Reformation, at least in Henry's lifetime.”