On the decease of the Emperor Kōtoku, after a reign of ten years, the previous empress, Kōkyoku, reassumed the scepter under the name of Saimei. This was the first instance of a sovereign occupying the throne twice. Prince Naka-no-ōye, who throughout both reigns had remained heir-apparent, succeeded the Empress Saimei under the name of Tenchi. This sovereign, who before ascending the throne had greatly distinguished himself, is not noted for any conspicuous deeds while in possession of the scepter. Throughout his reign the country enjoyed profound internal tranquillity. Its foreign affairs, however, assumed a complexion worthy of special notice. Since the conquest of southern Korea, which tradition attributes to the Empress Jingō, its kingdoms not only rendered tributes of valuable articles, but also conferred no small benefit on their suzerain by contributing to the latter's material and moral civilization. Nevertheless, the interval that separated the two countries made communication difficult, and although Japan established a branch government in Korea at a place called Mimana, the Koreans, relying upon the distance of the latter from headquarters, frequently acted in a rebellious manner. During an interval of 460 years after the legendary invasion of the Empress Jingō, no less than thirty instances are recorded when the Koreans either failed to send tribute, insulted Japanese envoys, or broke into open revolt. On every occasion Japan sent embassies to demand explanation and redress, or reasserted her supremacy by force of arms. Shiragi, which in those days stood at the head of the districts into which Korea was divided, rose in 562 against Mimana and succeeded in expelling the Japanese officials and obtaining possession of the place. This disaster weighed greatly on the mind of the Emperor Kimmei, whose last behest uttered on his deathbed was that Mimana should be recovered. A great army was accordingly sent against Shiragi, but success did not attend the Japanese arms. Not only was it found impossible to reduce Shiragi, but even the maintenance of the local government at Mimana proved a task beyond the military strength of the time. Thenceforth the recovery of Mimana became an object upon which Japan's attention was ever concentrated. When in 618 China fell under the powerful sway of the T'ang dynasty, the people of Shiragi, relying on Chinese assistance, conceived the project of bringing under their rule the neighboring district of Kudara. Reduced to extremities, Kudara in 660 sent envoys to seek succor from Japan. After considerable discussion, the Japanese Government resolved to undertake an expedition against Shiragi on a large scale. Great preparations were set on foot. The sovereign himself proceeded to Tsukushi and oversaw the dispatch thence of a fleet of a hundred war vessels under the command of Azumi-no-Hirafu, whose instructions were to attack Shiragi and rescue Kudara. But the latter was found to be in a helpless condition.