The separation of the Church of England from the Roman Catholic Church was primarily caused by King Henry VIII's desire for an annulment of his marriage to Catherine of Aragon. In the early 16th century, Pope Clement VII refused to annul the marriage, largely due to political pressures from Catherine's nephew, Holy Roman Emperor Charles V. Frustrated, Henry facilitated the English Reformation, declaring himself the Supreme Head of the Church of England through the Act of Supremacy in 1534. This separation allowed him to remarry and have male heirs, while also establishing a distinct English religious identity, which laid the groundwork for Protestantism's growth in England.