PROTESTANT DIETS. - Assemblies of religious-political representatives of the German states, of the primates of the Kingdom of Hungary, and of emissaries from Switzerland and the Scandinavian world. The principal D. were those of Augsburg (1518, 1530, 1547, 1555, 1686), Worms (1521, 1536), Nuremberg (1523, 1524), Speyer (1526, 1529, 1544), Cologne (1530), Frankfurt am Main (1539), and Regensburg (1542-1621).
At the D. of Worms, opened by Charles V on 28 January 1521, Luther took part in person, while the Pope was represented by two legates, later cardinals: Marino Caracciolo (1459-58), charged with political affairs, and Girolamo Aleandro (1480-1542) with ecclesiastical ones. At the D. of Nuremberg of 1522, prayers and processions were ordered, and a tax was also imposed to ward off the Turkish threat. The papal legate was Francesco Chieregati. At the first D. of Speyer, in the summer of 1526, the Protestant princes dared for the first time to proclaim their dissenting faith and to demand the convocation of a general or national council to resolve the ecclesiastical question raised by the irruption of Luther's reform. The impending Turkish invasion and the friction between the Emperor and the Pope favored this bold stance of the Lutherans, whereby every Protestant prince from then on claimed and exercised the so-called right to reform religion, ius reformandi religionem. From this there gained currency the maxim, antispiritual and anti-individual, according to which the political head of a territory is also its religious head: Cuius regio, eius et religio. At the D. of Augsburg of 1530, held in the presence of Emperor Charles V, on 24 June the papal nuncio Lorenzo Campeggio, while in Vienna the prayers of the muezzin could be heard from the tower of St. Stephen's, admonished the German states not to detach themselves from the Catholic Church and invited them to imitate the example of the other Catholic sovereigns. The next day Dr. Bayer, vice-chancellor of electoral Saxony, instead read the Augsburg Confession, which was then signed by seven princes.
Fifteen D. were held in Germany between 1848 and 1872, by the representatives of German evangelical or positive Protestantism: Wittenberg (1849), Stuttgart (1850), Elberfeld (1851), Bremen (1852), Berlin (1853), Frankfurt (1854), Lübeck (1856), Stuttgart (1857), Hamburg (1858), Barmen (1860), Brandenburg (1862), Altenburg (1864), Kiel (1867), Stuttgart (1869), and Halle (1872). They set out to "heal the divorce" between the ideas and the life of a great part of the nation and the doctrines of the Gospel, to bind the faithful in communion with one another as members of the one body of which Christ is the head, and to create a center of action in order to bring, wherever necessity required, the remedies indicated by the word of God. The program, however, was thwarted by the profound divergences existing among the Lutherans, the members of the so-called positive union, and those of the center party (Mittelpartei). And so the ecclesiastical d. no longer took place.