The Turkish invasion had meantime become more serious than the Saracenic conquests, as the invaders had now penetrated by land and sea respectively as far as Albania and Dalmatia. The pope once more urged Louis of Hungary, the successors of the crusading nobles who still held territory in Greece and along a portion of the coast of the Adriatic, the knights of Rhodes, and the king of Sicily to combine in a great movement with John against the common enemy. Once more he caused a new Crusade to be preached and promised indulgences to those who took up the Cross. He begged the Emperor Charles to make peace with Bavaria so that the empire in the West might join the Crusade. On all sides, however, there was a reluctance to enter upon it. In spite of the pope’s influence and promise to arm twelve galleys for despatch against the Turks, John’s ambassador returned from the West having completely failed in obtaining aid. Gregory the Eleventh was equally persevering in his efforts to bring about the Union of the Churches. Franciscan and Dominican missionaries were sent into the East to expose the wickedness of the schism caused or persisted in by the Orthodox Church. Nuncios were despatched to complete the reconciliation. The emperor was reproached, quite unjustly, because he was unable to persuade or compel his subjects to accept Union and to become reconciled with the Latin priests. The pontiff, however, did not lose sight of his political object. Louis of Hungary fell under his condemnation because he had neglected to engage in the Crusade. But Louis had seen the great defeat of Bulgaria and Southern Serbia on the Maritza in 1371 and was not prepared to make war hastily against so formidable a foe as the Turk had then shown himself to be. In 1374 the pope returned to the charge and urged the king of Hungary to be on watch against the incursions of the Turks into the empire until the fleet prepared at the pontiff’s expense should arrive in the Marmora. At the same time he invited John once more to visit Rome in order to discuss measures for the accomplishment of Union. In 1375 he again urged Louis of Hungary to do his duty as chief of the Crusade. He sent five hundred knights of Rhodes and an equal number of squires to defend the Greeks. He authorised the bishops in Western lands to apply large sums from the Church revenues for the purpose of resisting the enemy of Christendom. His influence fell far short of his desire. The Hungarian king was reported to have misappropriated the money he had been allowed to acquire from the Church, and the great fleet which the Genoese had collected for the purpose of attacking the Turks endeavoured to depose John in favour of his son Andronicus. [Sidenote: Difficulties with Sultan Murad.]