The bull officially excommunicating Luther, Decet Romanem Pontificem, was drafted on January 3, 1521, but as a mere formality. The previous bull threatening Luther’s excommunication, Exurge Domine, gave him sixty days to recant in person in Rome. On the sixtieth day after receiving the bull, December 10, he celebrated the occasion by burning the bull and the books of canon law along with it in a symbolic gesture that he was no longer under papal authority. John Eck, professor of theology at Ingolstadt, and Jerome Aleander, papal nuncio to emperor Charles V, were charged with promulgating Exurge Domine in German lands and it was Aleander himself who advised Charles in December of 1520 that Luther was already excommunicated on account of his failure to recant during the window provided him. Consequently, Luther’s excommunication was a foregone conclusion and awaited only official confirmation from Rome.
The bull itself, drafted on January 3, extended its reach far beyond simply excommunicating Luther. In addition to Luther, it also named three other sympathizers (the Nuremberg humanist Willibald Pirckheimer, knight and satirist Ulrich von Hutten, and Nuremberg clerk and reformer Lazarus Spengler) as excommunicates. The bull furthermore threated all those who protected Luther, read his books, or supported his reform with the same fate. It commanded that the verdict of excommunication be pronounced throughout the church within three days of receipt. Rome did not offer additional theological reasons for the decision, but instead based it on Luther’s unwillingness to recant within the time period established by the previous bull and therefore roots his condemnation in the same theological errors addressed in Exsurge Domine.
Decet Romanem Pontificem was delivered to Charles V on January 18, as he was preparing for the Diet of Worms, set to open on 28 January. Charles had in December revoked Luther’s invitation to defend himself at the diet, though Frederick the Wise eventually persuaded him to arrange for what would be his historic hearing in Worms. In the meantime, Aleander was responsible for publishing the bull in Germany, but he refrained from doing so until October 1521 for several reasons. First, he thought naming other parties in addition would provoke a greater reaction. Second, he had come to believe that support for Luther combined with opposition to Rome would threaten the stability of both church and empire in German lands. His instincts proved correct, as the bull was defaced when posted in several places. Many places proceeded with the requisite burning of Luther’s books, however, most notably Mainz, Leipzig, and Halberstadt, among others.