The age of the Crusades was indeed over. Frederick, in justifying his action to the princes of Europe, pointed to the conduct of the Papacy to Raymond of Toulouse and John of England as a warning to secular princes, and attributed the papal hostility not to a desire for the promotion of a crusade, but to greed. Gregory's conduct seemed to bear out this interpretation of his motives. Despite the excommunication Frederick once more set sail in June, 1228. But an expedition under such circumstances was an independent act subversive of all ecclesiastical discipline. Consequently, instead of his departure being the signal for the removal of his sentence, Frederick was followed to Palestine by the anathema of the Church. The Pope having got Frederick into his power intended to keep him there. Thus when Frederick reached Palestine the Templars and Hospitallers held aloof, while the Mendicant Orders preached against him; and when, in accordance with his treaty with the Sultan, he entered Jerusalem, the city and all the holy places were laid under an interdict. But Frederick was not daunted. Since no ecclesiastic would crown him he took the crown himself off the altar and placed it on his head. For as in the case of the Pope, so with Frederick, it was from no religious motives that he persisted in the crusade. It was a purely political expedition. He put the Pope in the wrong in the eyes of European princes by refuting the charge of the Roman supporters that he never seriously intended to go on crusade. But, more important still, his own attitude and act were a manifesto on behalf of the Empire against the claim put forward by Innocent III for the Papacy as the head and leader of Christendom. But the very means of his success added to his enormities. It was nothing that he had gained for Christendom without fighting more than had been won since the First Crusade. For he had dealt with the Sultan of Egypt as an equal, and in the treaty which gave him Jerusalem and several other places he had undertaken to enforce certain articles favourable to the Sultan, even in the event of opposition from Christian Princes. Thus it is not astonishing that while Frederick was winning this success in Palestine Pope Gregory was using papal emissaries, in the shape of the lately founded Orders of mendicant friars, to denounce the Emperor in every country of Western Europe, and even let loose on Frederick's Sicilian territories an army of so-called crusaders under John of Brienne, who resented the adoption of the title of King of Jerusalem by his imperial son-in-law. This monstrous attack upon a successful crusader turned the sentiment of Europe against the Pope. Frederick returned in June, 1229, and by the help of his Saracen troops drove out the invaders. In return for peace with the Church Frederick was willing to give to the Pope almost extravagantly generous terms, and a treaty was arranged at San Germano