Composed for the Feast of the Reformation, celebrated annually on October 31, this is arguably the best known of all of Bach’s cantatas.  Employing the most famous of all Lutheran chorales, “Ein feste Burg ist unser Gott” (A might fortress is our God), a chorale written by Luther himself, Bach’s congregation at Thomaskirche would definitely have known this melody by heart.  First performed between 1727 and 1731, it was probably composed either in 1723 or between 1728 and 1731. It is based on the earlier cantata Alles, was von Gott geboren, which was produced in Weimar in 1715 or 1716 for the fourth Sunday after Easter.  This was also the first of Bach's cantatas to be published after his death. The Bach Gesellschaft edition did note appear until half a century later, and included an extended instrumentation by Wilhelm Friedemann. Extremely rare, we have traced only one copy appearing at auction, in 1953. Worldcat records 5 copies, all in Germany. 

No more than a few works by Johann Sebastian Bach were printed during his lifetime, including only a single cantata published early in his career.  Christoph Wolff has suggested three reasons: firstly the financial support from municipal councils or noble patrons available to previous generations had diminished in Germany as a result of the Thirty Years War; secondly the expense of printing contrapuntal keyboard music which, at that time in Germany, was more often typeset than engraved; and lastly the low number of potential customers for works that were often technically difficult and unconventional.   Especially the choral works, less than half a percent of over 400 BWV numbers, are under-represented. This was however not exceptional for Bach's time when larger works for chorus and orchestra were less often printed. Bach's own efforts to get his works printed concentrated mostly on his keyboard compositions, which contributed to the fact that, at least until the 19th-century Bach Revival, he was mainly regarded as a keyboard composer.