We have now come to the events which marked the rise of the great Yŭn power in Liao-tung. They are so intimately connected with the history of Ko-gu-ryŭ that we must give them in detail. For many years there had been a Yŭn tribe in the north but up to the year 320 it had not come into prominence. It was a dependency of the Tsin dynasty of China. Its chiefs were known by the general name Mo Yong. In 320 Mo Yong-we was the acting chief of the tribe. He conceived the ambitious design of overcoming China and founding a new dynasty. The Emperor immediately despatched an army under Gen. Ch’oe-bi to put down the incipient rebellion. Ko-gu-ryŭ and the U-mun and Tan tribes were called upon to render assistance against the rebels. All complied and soon the recalcitrant chieftain found himself besieged in Keuk Fortress and was on the point of surrendering at discretion when an event occurred which, fortunately for him, broke up the combination and raised the siege. It was customary before surrendering to send a present of food to the one who receives the overtures of surrender. Mo Yong-we, in pursuance of this custom, sent out the present, but for some reason it found its way only into the camp of the U-mun forces while the others received none. When this became known the forces of Ko-gu-ryŭ, believing that Mo Yong-we had won over the U-mun people to his side, retired in disgust and the Chinese forces, fearing perhaps a hostile combination, likewise withdrew. The U-mun chiefs resented this suspicion of treachery and vowed they would take Mo Yong-we single-handed. But this they could not do, for the latter poured out upon them with all his force and scattered them right and left. From this point dates the rise of Yŭn. Gen. Ch’oe-bi fearing the wrath of the Emperor fled to Ko-gu-ryŭ where he found asylum. Here the affair rested for a time. The kingdom of Yŭn forebore to attack Ko-gu-ryŭ and she in turn was busy strengthening her own position in view of future contingencies. Ten years passed during which no events of importance transpired. In 331 Eul-bul the king of Ko-gu-ryŭ died and his son Soé began his reign by adopting an active policy of defense. He heightened the walls of P’yŭng-yang and built a strong fortress in the north, called Sin-sŭng. He followed this up by strengthening his friendly relations with the court of China. These facts did not escape the notice of the rising Yŭn power. Mo Yong-whang, who had succeeded Mo Yong-we, hurled an expedition against the new Sin-sŭng Fortress and wrested it from Ko-gu-ryŭ. The king was compelled, much against his will, to go to Liao-tung and swear fealty to the Yŭn power. Two years later the capital was moved northward to Wan-do, in the vicinity of the Eui-ju of today. This was done probably at the command of Yŭn who desired to have the capital of Ko-gu-ryŭ within easy reach in case any complications might arise.