The opportunity to the Christians seemed tempting. News had arrived that a powerful fleet of seventy ships had appeared in the Bosporus, ten triremes having been sent by the pope and ten others at his request by Latin princes. The duke of Burgundy and a French cardinal had arrived at Constantinople to urge John to join in a Christian league. The cities of Thrace were undefended by the Turks, and the fleets, it was believed, could prevent Murad with his army from crossing into Europe. The only obstacle to vigorous and successful action was the newly signed treaty. Pretexts were found that Ladislaus had had no right to agree to a truce without the consent of the pope, and that Murad had not executed his part of the treaty. Ladislaus hesitated to break his oath, but Cardinal Julian urged that his league with the Christian princes of the West was better worth respecting than his oath to the miscreant. According to more than one author, he maintained the proposition that no faith need be kept with infidels.[142] Finally, the cardinal called down upon his own head all punishment due to the sin, if sin there were, in violating the oath. But in the name of the pope, the vicar of God on earth, he formally released the king from the obligations to which he had sworn.[143] The action of Ladislaus was in reality not merely wicked and immoral, but ill-advised and hasty. Even in the short interval between the conclusion of peace and the declaration of war, the French, Italian, and German volunteers had gone home. John was not ready to aid him. Phrantzes had been sent to Ladislaus, to the cardinal, and even to the sultan, to temporise and to prevent an outbreak of war before a coalition could be formed. Hunyadi very reluctantly gave his consent to the violation of the truce, and then only on condition that the declaration of war should be postponed until September 1. George of Serbia not only refused to violate the engagement into which he had solemnly entered with Murad but refused to permit Scanderbeg to join Ladislaus. The whole business was ill-considered and ill-managed, and the fault lies mainly with the cardinal.