Nicholas confined himself to a few exhortations addressed to the faithful, and died without having removed any of the difficulties which opposed themselves to the undertaking of a holy war. Calixtus III., who succeeded him, showed more zeal, and at the very commencement of his pontificate, he sent legates and preachers throughout Europe, to proclaim a crusade and levy tenths. An embassy from the pontiff went to solicit the kings of Persia and Armenia, and the khan of the Tartars, to unite with the Christians of the West, to make war against the Turks. Sixteen galleys, constructed with the produce of the tenths, put to sea under the command of the patriarch of Aquileia, and displayed the banner of St. Peter in the Archipelago, and on the coasts of Asia Minor; Æneas Sylvius harangued the pope in the name of the emperor of Germany, and promised him the concurrence of all the powers of Christendom, if his holiness opened the treasures of the Church, and, by his evangelical exhortations, called _all the workmen to the harvest_. Calixtus III. thanked the head of the empire for his advice, and pressed him to set the example. But the indolent Frederick contented himself with renewing his promises; and whilst the emperor was thus exhorting the pope to maintain a crusade, and that the pope, on his side, was urging the emperor to take arms, the Ottomans penetrated into Hungary, and advanced against Belgrade. This city, one of the bulwarks of the West, received no succour from Christendom. There remained no hope for it but in the valour of Hunniades, and in the apostolic zeal of John of Capistran. The one commanded the troops of the Hungarians, and excited them by his example; the other, who, by his preachings had got together a great number of German Crusaders, animated the Christian soldiers, and inspired them with an invincible ardour. Contemporary chronicles inform us, that at this period a hairy comet appeared blazing in the east. The Christian nations believed they saw in this phenomenon a prophetic signal of the greatest evils; and as the evil then most to be dreaded was the invasion of the Turks, Calixtus was desirous of profiting by this feeling of the people, to revive the idea of a crusade. He exhorted the Christians to penitence; and pointed out the holy war as a means by which they might expiate their sins and appease the anger of Heaven. In no country, notwithstanding, did the people arm, except in those that were immediately menaced by the Turks. It was at this time that the pope ordered that every day at noon, the bells should be rung in all parishes, to call upon the faithful to pray for the Hungarians, and for those who were contending with the Turks. Calixtus granted indulgences to all Christians who, at this signal, would repeat the Dominical prayer and the angelic salutation three times. Such was the origin of the _Angelus_, which the customs of the Church have consecrated, and continued to modern times.