Final answer:
Martin Luther, a German monk, initiated the Protestant Reformation in the 16th century by posting the '95 Theses' on the door of a church in Wittenberg. His protest against the Roman Catholic Church led to the division of European Christianity and the formation of new Protestant sects.
Step-by-step explanation:
Martin Luther, a German monk and professor of theology, launched the Protestant Reformation in the 16th century as a protest against the Roman Catholic Church. He compiled a list of concerns known as the '95 Theses' and nailed it to the door of a church in Wittenberg, Germany. This act led to the unintended consequence of splitting European Christianity and ultimately resulted in the formation of new Protestant sects. While Luther's actions did not fully reform the Catholic Church, they initiated significant changes and laid the groundwork for subsequent religious movements.