But all of this, like his projected coalition with the Swiss, was prevented from succeeding by the jealousy prevailing between Duke Maurice of Saxony and the Elector John Frederick I of Saxony. Fearful of the success of these plans, the emperor invited Philip to an interview at Speyer. Philip spoke plainly in criticism of the Emperor's policy, and it was soon evident that peace could not be preserved. Four months later (20 July 1546) the imperial ban was declared against John Frederick and Philip as perjured rebels and traitors. The result was the Schmalkaldic War, the outcome of which was unfavorable to Protestant interests. The defeat at the Battle of Mühlberg in 1547 and the capture of the Elector John Frederick marked the fall of the Schmalkaldic League.