Luther died on 18 February 1546 . The death of his longtime friend and colleague plunged Melanchthon into mourning and he was very concerned about the solidarity of the Protestant side. The Council of Trent was not recognized by the Protestants, and the religious discussion at the Diet of Regensburg was inconclusive. What many had feared for a long time finally happened in July: Emperor Charles V declared war on the Schmalkaldic allies. Although many students left Wittenberg, lectures at the university did continue, but in November the Leucorea was closed and Melanchthon retired to Zerbst.