Under Kaotsong the power of the Tangs showed for thirty years no diminution, and he triumphed in directions where his father had only pointed the way to victory. He began his reign with a somewhat risky act by marrying one of his father's widows, who then became the Empress Won. She was perhaps the most remarkable woman in the whole range of Chinese history, acquiring such an ascendency over her husband that she practically ruled the state, and retained this power after his death. In order to succeed in so exceptional a task she had to show no excessive delicacy or scrupulousness, and she began by getting rid of the other wives, including the lawful empress of Kaotsong, in a summary fashion. It is stated that she cast them into a vase filled with wine, having previously cut off their hands and feet to prevent their extricating themselves. But on the whole her influence was exerted to promote the great schemes of her husband. The Tibetan question was revived by the warlike proclivities of the new Sanpou, who, notwithstanding his blood relationship with the Chinese emperor, sought to extend his dominion at his expense toward the north and the east. A desultory war ensued, in which the Chinese got the worst of it, and Kaotsong admitted that Tibet remained "a thorn in his side for years." A satisfactory termination was given to the struggle by the early death of the Sanpou, whose warlike character had been the main cause of the dispute. Strangely enough the arms of Kaotsong were more triumphant in the direction of Corea, where his father had failed. From A.D. 658 to 670 China was engaged in a bitter war on land and sea with the Coreans and their allies, the Japanese, who thus intervened for the first time in the affairs of the continent. Owing to the energy of the Empress Wou victory rested with the Chinese, and the Japanese navy of four hundred junks was completely destroyed. The kingdom of Sinlo was made a Chinese province, and for sixty years the Coreans paid tribute and caused no trouble. In Central Asia also the Chinese power was maintained intact, and the extent of China's authority and reputation may be inferred from the King of Persia begging the emperor's governor in Kashgar to come to his aid against the Arabs, who were then in the act of overrunning Western Asia in the name of the Prophet. Kaotsong could not send aid to such a distance from his borders, but he granted shelter to several Persian princes, and on receiving an embassy from the Arabs, he impressed upon them the wisdom and magnanimity of being lenient to the conquered. Kaotsong died in 683, and the Empress Wou retained power until the year 704, when, at the age of eighty, she was compelled to abdicate. Her independent rule was marked by as much vigor and success as during the life of Kaotsong. She vanquished the Tibetans and a new Tartar race known as the Khitans, who appeared on the northern borders of Shensi. She placed her son in confinement and wore