("A Mighty Fortress Is Our God"), BWV 80 (also: BWV 80.3), is a chorale cantata for Reformation Day by Johann Sebastian Bach. He reworked it from one of his Weimar cantatas, Alles, was von Gott geboren, BWV 80a (also: BWV 80.1). The first Leipzig version of the church cantata, BWV 80b (also: BWV 80.2), may have been composed as early as 1723, some five months after Bach had moved to Leipzig. Some years later he reworked the cantata one more time, writing an extended chorale fantasia as its opening movement. The text of the BWV 80a version was written by Salomon Franck and contained one stanza of Martin Luther's hymn "Ein feste Burg ist unser Gott"; for his chorale cantata versions, BWV 80b and 80, Bach added the complete text of this Lutheran hymn. Bach scored the cantata for four vocal soloists, a four-part choir and a Baroque chamber ensemble of up to three oboes of different kinds, strings and continuo. After his death, his son Wilhelm Friedemann Bach arranged the first and fifth movements, adopting a new text and adding trumpets and timpani. was published in 1821, the first of Bach's cantatas published after his death. The Bach Gesellschaft edition appeared half a century later, and included an extended instrumentation by Wilhelm Friedemann. History and composition Bach wrote the cantata in Leipzig for Reformation Day, celebrated annually on 31 October. In composing this work, Bach reused an earlier cantata, Alles, was von Gott geboren, BWV 80a, which he wrote in Weimar for the third Sunday in Lent and based on a text published in 1715 by Salomon Franck. This work, on which the Leipzig versions were based, was one of a few in which Bach quoted the same hymn twice, in a closing chorale and in an instrumental cantus firmus in the opening movement. In BWV 80a, he used the second stanza of Luther's hymn "Ein feste Burg ist unser Gott" ("A Mighty Fortress Is Our God"), which is "Mit unser Macht ist nichts getan" (With our might nothing is done), for the closing chorale. Bach could not use the earlier work at its intended time in Leipzig, because cantata music was prohibited there during Lent. The early Leipzig version (BWV 80b) began with a simple chorale setting of the hymn as the opening movement. This is the only version of the cantata of which autograph pages survive. However,