It seems to have been generally recognised that young Mahomet, the successor of Murad, had even before his accession determined to lay siege to the city. The emperor, therefore, once more renewed the efforts of his predecessors to obtain foreign aid. Once more the insuperable obstacle to the Union of the Churches, the rigid refusal of clergy and people, came to the fore. Constantine, like his predecessors, tried and failed to coerce the Church. Athanasius, the new patriarch, declared himself ready to maintain the Orthodox faith and declined to recognise the acts of the Council of Florence. When Constantine asked aid from Rome, he found that the deposed Gregory had taken refuge there, and while the patriotism of the latter led him to seek the pontiff’s help against the Turks, his Catholicism compelled the pope to espouse his cause. Nicholas the Fifth summoned the emperor, as the price of his support, to replace Gregory and to take the measures necessary for formally completing the Union agreed to at Florence. Constantine was willing to do what he could, but knew the temper of his subjects. He knew himself to be distrusted by them for what they regarded as his Romanising tendencies. When Mahomet was at Magnesia, where the news of the death of his father reached him, the Christians around regarded the new emperor unfavourably on account of his predilection for the Union, and spoke of him as a usurper. Constantine, who was on the look out for a wife[187] and had employed Phrantzes on various expeditions to find one, had been compelled, on account of the opposition of his subjects to any further relationship with the Latins, to abandon his intention of marrying the daughter of Foscari, the doge of Venice. He had thus given offence to a powerful state, and, though he had offered all sorts of concessions, Venice would only promise to send ten galleys to the help of the city. The emperor temporised. He begged the pope to send ships and also learned and capable ecclesiastics who could aid him to make the Union acceptable to the clergy. In reply Nicholas promised to send a fleet, although he was powerless to persuade other Christian princes to follow his example. In answer to his second request he deputed Cardinal Isidore, Metropolitan of Russia, whom we have seen at the Council of Florence, to be his legate.