After a time the Emperor fretted under this position of vassalage, and in 1369 he went on a mission to Rome, in the hope of inducing the Pope to stir up the Christian Powers of Europe to another crusade against the Ottomans. He left his eldest son, Andronicus, in charge of the government at Constantinople during his absence. Arriving at Rome, he submitted to the most humiliating conditions with the object of gaining the support of the Pope Urban V. He abjured at St. Peter’s, before the High Altar, the principles of the Greek Church, so far as they differed from those of Rome. He admitted the ecclesiastical supremacy of the Pope. He was then permitted to bend his knee, and to kiss the Pope’s feet and hands. He was privileged also to lead the Pope’s mule by the bridle. He obtained, however, no return for these abject humiliations. The Pope was unable to induce the Christian Powers again to take up arms against the Ottomans. The Emperor’s concessions to the Pope were also disavowed by the Hierarchs of the Greek Church at Constantinople. There never was any prospect of a reunion of the two Churches. The Emperor, John Palæologus, embarked on his homeward journey having nothing to show for his pains. On his way back, when passing through Venice, he was arrested, at the instance of his Venetian creditors, who had lent him money to defray the cost of his mission. Not having the means to pay, he could not discharge the legal process. Andronicus had no wish that his father should ever return to Constantinople. He made no effort to raise money for the release of the Emperor. He pleaded the poverty of the Treasury. A younger son, Manuel, however, with more filial piety, raised the necessary sum, by selling all his property, and obtained the release of his father. Shortly after his return to Constantinople the Emperor, as was to be expected, deprived Andronicus of all his appointments, and replaced him by Manuel, whom he also made co-Emperor with himself. The son of Andronicus, of the same name, furious at this treatment of his father, entered into a mad conspiracy with Saoudji, the youngest son of Sultan Murad, with the object of dethroning both Emperor and Sultan and reigning in their place. Saoudji, being in command of the Sultan’s army in Europe, during the absence of Murad in Asia, was able to tamper with the loyalty of the Ottoman troops. He assembled a considerable force in the neighbourhood of Constantinople, where he was joined by a large number of the sons of Greek nobles and by many soldiers.