Prelude on the Babylonian Captivity of the Church (Latin: De captivitate Babylonica ecclesiae, praeludium Martini Lutheri, October 1520) was the second of the three major treatises published by Martin Luther in 1520, coming after the Address to the Christian Nobility of the German Nation (August 1520) and before On the Freedom of a Christian (November 1520). The book-length work was theological, and as such was published in Latin as well as German, the language in which the treatises were written. Source: Wikipedia (en)