The movement initiated from Hungary put heart into the Byzantines, who, because of the change from the mild Murad to the relentless Bajesid, were now hard pressed in the small corner of territory still left them. There was moral depression as well, for Manuel II, when made co-Emperor with his aged father John, had been obliged to accompany the Sultan in all his campaigns with a contingent. This obligation revealed the desperate straits of the Greek Empire, especially as the contingent numbered only a hundred men. One Greek city, Philadelphia, the single imperial possession in Asia Minor, had been attacked by Bajesid because the citizens refused to receive a Turkish garrison, though John had previously agreed to surrender it to Murad. Among the other vassals who were called to take part in this campaign were Stephen, Prince of the Servians, and Manuel, the Byzantine Emperor. As a further sign of dependence on the Sultan’s will, who seemed bent on devising schemes to humiliate the miserable Greek prince, Manuel had been forced to help to repair the fortifications of Gallipoli, and also to coöperate with the Turks in their preparations to send expeditions to Attica and some of the islands of the Ægean. When John V began to restore some of the ruined fortifications around the imperial city, Bajesid ordered him to desist, threatening, if the command were not obeyed, to deprive Manuel of his sight, for the heir, and co-Emperor, was, as usual, doing duty as a vassal in one of the Turkish military expeditions. On the death of John V, in 1391, Manuel was allowed to succeed to the title, and, officially, good relations were observed between the Sultan and the ruler of Constantinople. Bajesid, however, had no intention of permitting Manuel, whom he knew to be a man of ability and decision, to gain any new ground. The few places contiguous to Constantinople, over which the Greeks still ruled, were constantly being harassed by Ottoman aggressions. Manuel was really being besieged in his own capital. His constant appeals for help were made in vain; the Venetians found it commercially more advantageous to draw closer to the Osmanlis, especially since Bajesid, by absorbing various emirates in Asia Minor, was in control of important trading towns on that coast. A treaty was concluded between the two powers, and the Venetians went so far as to deny their help to the Frankish lords of the Ægean, and were preparing to weaken continental Greece by efforts to gain territory in that quarter at the expense of the Greek master of the Morea, a son of the Emperor.