While successful on land Mousa was defeated at sea, and the inhabitants of the capital, in 1411, saw the destruction of his fleet off the island of Plataea in the Marmora. In revenge for this defeat he laid siege to the city. Manuel and his subjects stoutly defended its landward walls, and before Mousa could capture it news came of the revolt of his younger brother, Mahomet, who appeared as the avenger of Suliman. The siege of Constantinople had to be raised. Mahomet had taken the lordship of the Turks in Caramania shortly after the defeat of his father at Angora, and had been unattacked by Timour. The emperor proposed an alliance with him, which was gladly accepted and the conditions agreed to were honourably kept by both parties. Mahomet came to Scutari where he had an interview with the emperor. An army formed of Turks and Greeks was led by Mahomet to attack his brother. But Mousa defeated him in two engagements. Then Manuel, after a short time, having been joined by a Serbian army, attempted battle against him, and with success. The Janissaries deserted Mousa and went over to Mahomet and Manuel, and his army was defeated. He was himself captured and by order of Mahomet was bowstrung.[126] [Sidenote: Sultan Mahomet the First, 1413–1420.] Mahomet was now the only survivor of the six sons of Bajazed, with the exception of Isa, the youngest, who was still living with Manuel as a hostage. Three of his brothers had been the victims of fratricide. In 1413, Mahomet proclaimed himself Grand Sultan of the Ottomans. He had been loyally aided by Manuel and the Serbians, and in return loyally respected the agreements he had made with both. He gave up, as we have seen, Salonica and the fortified towns on the Euxine, the Marmora and in Thessaly which had been taken from the Greeks. In 1415, the Turks, who had remained nearly undisturbed on the western side of the Balkans, entered Bosnia. The inhabitants were mostly Bogomils, who had been constantly persecuted by their Catholic neighbours in order to force them to Union with the Church of Rome, were menaced, on account of their refusal, by the king of Hungary, and in reply threatened that they would coalesce with the Turks. Upon such an intimation, the Turks entered the country.[127] The two rulers, Manuel and Mahomet, continued on friendly terms. It was probably due to the emperor’s influence that the sultan consented, in 1415, to allow the Knights of Rhodes to build a strong fortification on the boundaries of Caria and Lycia as a place of refuge for Christians who should escape from the hands of the Moslems. Ducas gives an account of the interview which took place between the grand master and Manuel and adds that the emperor went so far towards conciliating the Christians that he contented the rulers of Chios, Mitylene, and Phocaea. In returning from the Morea in 1416, Manuel met Mahomet at Gallipoli, the sultan going on board Manuel’s galley and eating with him. [Sidenote: Death of Mahomet.]