The 14–15 th-century unrest led to a desire for religious reform and a return to Christian basics. Initiated in 1517 by Martin Luther in Germany, the Reformation rejected the Pope’s and the clergy’s spiritual superiority and believed that only faith in God led to salvation. Other reformers, such as Bucer, Zwingli and Calvin developed these ideas inspired by Luther. The Reformation affected most of north-western Europe and led to fierce battles during the 16th and 17th centuries, known as the European Wars of Religion. The Catholic Church responded with a counter-reformation decreed at the Council of Trent.