After the death of Paul II., who had not time to achieve his work, and did not witness the effect of his preachings, his successor, Sextus IV., neglected nothing for the defence of Christendom. When scarcely seated on the pontifical throne, he deputed cardinals to several states of Europe, to preach peace among Christians and war against the Turks. The legates were specially intrusted to press the levying of the tenths for the crusade. They were authorized to launch the thunders of excommunication against those who should oppose this impost, or who misapplied the produce of it. This severity, which occasioned troubles in England, and still more in Germany, succeeded in other countries, and furnished the sovereign pontiff with means for preparing for war. But none of the princes of the West took up arms, and Christendom was still exposed to the greatest perils, when fortune sent succour it had no reason to look for from the depths of Asia. Of all the powers that had promised to combat the Ottomans, the only one that did not fail, was the king of Persia, to whom Calixtus III. had sent a missionary, and who declared himself the faithful ally of the Christians. In his reply, the king of Persia bestowed the greatest praises on the pope, encouraged him in his resolution of attacking Mahomet, and announced to him that he himself would commence hostilities. At the time his letter was received at Rome, his troops were already crossing Armenia, and several Ottoman cities had fallen into the hands of the Persians. Mahomet was obliged to abandon or to suspend his projects of conquest on the side of Europe, to march against these new enemies, with the greater part of the strength of his empire.