The Protestant Reformation in Europe in the first half of the 16th century challenged the Roman Catholic Church. Before Martin Luther publicized his “95 Theses,” almost all Europeans belonged to the Catholic Church. Just 20 years later, many Europeans belonged to the Reformed, or Protestant, church. The Catholic Church responded during a period known as the Counter-Reformation.
Reforming the Catholic Church
The Catholic Church accepted some Protestant criticisms as valid. They held sessions of the Council of Trent to tackle these issues. The council examined the corruption plaguing the church, including the sale of indulgences, a system in which rich people could buy forgiveness for their sins. The council defined many important aspects of church life, such as the number of sacraments.
The Church established new organizations as part of the reaction to the Reformation. Some organizations were open to both clerics and lay people. Others were only open to clerics. One important example is the Society of Jesuits, which became responsible for creating Catholic schools and colleges across the world to bring young people into the faith.
Catholic kings and princes established military expeditions to capture the territory of Protestant monarchs, as well as to enlarge their own estates. King Phillip II of Spain, backed by the king of France and Holy Roman Emperor Charles V, led a campaign against Protestants in present-day Belgium and the Netherlands, and England. His launched an armada of 122 ships to invade England, but it was defeated by a combination of the English navy and British weather.
Pope Paul III founded the Roman Inquisition in 1542 to deal with academic issues relating to theological thought. The Inquisition published an Index of Forbidden Books, effectively an act of censorship of what the church regarded as heretical writings. The Inquisition also executed people it judged to have broken the church’s rules. By 1580 Protestant resistance had been eliminated in Italy.
Source: How Did the Catholic Church Respond to the Challenges Posed by the Protestant Reformation?