Final answer:
Priests in Henry VIII's England were required to swear an oath to the Anglican Church or face severe consequences, including execution. This requirement was a part of the significant religious reforms that distanced England from Roman Catholic practices and strengthened the Anglican Church.
Step-by-step explanation:
Under the rule of Henry VIII, Thomas Cranmer and Thomas Cromwell influenced the monarch to separate from the Roman Catholic Church, leading to the formation of the Church of England, commonly known as the Anglican Church. As the head of the Church, the king required all priests to swear an oath of allegiance to the Church of England. Failure to do so had severe consequences, including execution. The subsequent monarch, Edward VI, further reformed the church to align more closely with Protestant practices, while Charles I faced opposition for his perceived Catholic sympathies and decisions which ultimately led to the English Civil War and his execution.