The Diet of Speyer was convened in March 1529, for action against the Turks, whose armies were pressing forward in Hungary, and would besiege Vienna later in the year, and against the further progress of Protestantism.
The Diet opened on 15 March. The Catholic dignitaries appeared in full force, as did various princes and representatives of imperial cities who were leaning towards Luther and Zwingli's reforms. Ascendant Roman Catholic forces, particularly given Charles V's recent successes against the French in Italy, aimed to reverse the policy of religious tolerance adopted in 1526.
The meeting was not attended by Charles. He sent instructions to his regent, Ferdinand, to pursue a conciliatory line, but his advice did not reach his brother in time. Instead, Ferdinand read out his own far less conciliatory suggestions in Charles's name at the start of the Diet. Ferdinand condemned the way many princes had interpreted the recess issued at Speyer in 1526. He specifically denied them the right to choose which religious reforms would take effect in their states, and ordered that Catholicism be followed in all states of the Holy Roman Empire.
The Protestants felt that "Christ was again in the hands of Caiaphas and Pilate." The resultant recess of the Diet neutralized the recess of the preceding Diet of 1526; it virtually condemned (without, however, annulling) the innovations made; and it forbade, on pain of the imperial ban, any further reformation until the meeting of the council, which was now positively promised for the next year by the Emperor and the Pope. The Edict of Worms was therefore to be enforced after all, without waiting for a General Council. The Zwinglians and Anabaptists were excluded even from toleration. The latter were to be punished by death.