1. The Protestant Reformation was a response to criticisms of corruption and doctrinal issues within the powerful Roman Catholic Church in the early 16th century.
2. Martin Luther's 95 Theses challenging the Church's sale of indulgences and doctrine of salvation through faith alone rather than works sparked the movement.
3. The printing press and vernacular Bible translations helped spread Protestant reforms by making scripture accessible to the masses rather than just clergy.
4. The Catholic Church held the Council of Trent to reaffirm traditional doctrines like transubstantiation and counter the Protestant challenge.