What act is generally referred to as the beginning of the Protestant Reformation?

The act that is generally referred to as the beginning of the Protestant Reformation is Martin Luther's nailing of his Ninety-Five Theses to the door of the Castle Church in Wittenberg, Germany, on October 31, 1517.

Here are the steps that led to this event:

1. Martin Luther, a German monk and professor of theology, was troubled by what he perceived as the corruption and abuses within the Catholic Church, particularly the sale of indulgences.

2. Indulgences were payments made by people to the Church as a form of penance for their sins. Luther believed that salvation could not be bought but was a gift from God.

3. On October 31, 1517, Luther wrote a letter to his bishop, Albert of Mainz, protesting the sale of indulgences. He included in his letter a copy of his "Disputation of Martin Luther on the Power and Efficacy of Indulgences," which came to be known as the Ninety-Five Theses.

4. Tradition holds that Luther also nailed a copy of his theses to the door of the Castle Church in Wittenberg, which served as a notice board for university-related announcements. This act is often cited as the start of the Protestant Reformation.

5. Luther's theses were quickly reprinted and spread throughout Germany and then Europe. This widespread dissemination of his ideas led to a break with the Catholic Church and the establishment of Protestant churches.