Marco Polo returned to the court of Kublai-Khan when he had finished the expedition of which we spoke in the last chapter. He was then entrusted with several other missions, in which he found his knowledge of the Turkish, Chinese, Mongolian, and Mantchorian languages of the greatest use. He seems to have taken part in an expedition to the islands in the Indian Ocean, and he brought back a detailed account of this hitherto little known sea. There is a want of clearness as to dates at this part of his life, which makes it difficult to give a correct narrative of these voyages in their right order. He gives a circumstantial account of the Island of Cipango, a name applying to the group of islands which make up Japan; but it does not appear that he actually entered that kingdom. This country was famous for its wealth, and about 1264, some years before Marco Polo arrived at the Tartar court, Kublai-Khan had tried to conquer it and sent his fleet there with that purpose. They had taken possession of a citadel and put all its valiant defenders to the edge of the sword, but just at the moment of apparent victory a storm arose and dispersed all the enemy's fleet, and thus the expedition was useless. Marco Polo gives a long account of this attempt, and adds many curious particulars as to Japanese customs. Marco Polo, with his father and uncle, had now been seventeen years in the service of Kublai-Khan, and even longer absent from their own country; they had a great wish to revisit it, but the Emperor had become so much attached to them, and valued their services so highly, that he could not make up his mind to part with them. He tried in every way to shake their resolution, offering them riches and honour if only they would remain with him, but they still held to their plan of returning to Europe; the Emperor then absolutely refused to allow them to go, and Marco Polo could find no means of eluding the surveillance of which he was the object, until circumstances arose which quite changed Kublai-Khan's resolution. A Mongol prince, named Arghun, whose dominions were in Persia, had sent an ambassador to the Emperor to ask one of the princesses of the blood royal, in marriage. Kublai-Khan acceded to his request and sent off his daughter Cogatra to Prince Arghun, attended by a numerous suite; but the countries by which they endeavoured to travel were not safe; the caravan was soon stopped by disturbances and rebellions, and after some months was obliged to return to the Emperor's palace. The Persian ambassadors had heard Marco Polo spoken of as a clever navigator who had had some experience of the Indian Ocean, and they begged the Emperor to confide the Princess Cogatra to his care, that he might conduct her to her future husband, thinking that the voyage by sea would probably be attended by less danger than a land journey.