In Protestant Reformation history, confessionalization is the parallel processes of "confession-building" taking place in Europe between the Peace of Augsburg (1555) and the Thirty Years' War (1618–1648). For most of this time, there was a nominal peace in the Holy Roman Empire between the Protestant and Catholic confessions as both competed to establish their faith more firmly with the population of their respective areas. This confession-building occurred through "social-disciplining," as there was a stricter enforcement by the churches of their particular rules for all aspects of life in both Protestant and Catholic areas. This had the consequence of creating distinctive confessional identities that influenced church dogma, faith formation, liturgy, and the development of universities.
The German historian Ernst Walter Zeeden first described the phenomenon of 'confession building' (Konfessionsbildung) in the 1950s. In the 1970s, Wolfgang Reinhard and Heinz Schilling further developed these ideas in parallel, applying their ideas to church-state formation in Roman Catholic and Lutheran contexts in the Holy Roman Empire.
