What movement began as an attempt to reform the Catholic Church and later led to its separation?

The Protestant Reformation began as an effort to address and reform certain practices and beliefs within the Catholic Church. Initiated by figures like Martin Luther in the early 16th century, it sought to correct perceived corruption, such as the selling of indulgences, and to reaffirm the authority of scripture over Church tradition. The movement gained traction and ultimately led to the establishment of various Protestant denominations that separated from the Catholic Church. This significant historical event not only transformed religious practices but also had profound social, political, and cultural effects across Europe and beyond.

The other movements and events mentioned, such as the Counter-Reformation and the Council of Trent, were responses to the Reformation, aiming to reaffirm Catholic doctrine and address some of the criticisms raised by reformers. The Orthodox Split refers to the division between the Eastern Orthodox Church and the Roman Catholic Church that occurred in the year 1054, which is unrelated to the reforms initiated in the 16th century.