Wang-gön looked out for the interests of the people in the distant parts of the country as well as for those near the capital. In order to break the force of the attacks of the wild people beyond the Tu-man River he built a wall across the northern border of Ham-gyŭng Province. It is said to have been 900 _li_ long. But there was a still stronger enemy on the south. Kyŭn-whŭn had by this time come to see that he had no hope of overcoming the young kingdom of Koryŭ and so he bent his energies to the securing of his position against the danger of interference, especially in his plans against Sil-la. For this reason he sent a messenger to Song-do with presents and tried to make friends with his old time enemy. His next move was to attack Sil-la. Wang-gön took up the cudgels in support of the king of Sil-la and by so doing secured the lasting enmity of the bandit who from this time determined upon war without quarter against his northern enemy. Wang-gön said to the Sil-la envoys, “Sil-la has three treasures; the nine storey pagoda, the Buddha six times the height of a man, and the jade belt. As long as these three remain intact Sil-la will stand. The first two are in Sil-la. Where is the jade belt?” The envoy answered that he did not know, whereupon Wang-gön blamed him sharply and sent him home. When Sil-la finally fell, the jade belt passed into the hands of Wang-gön. In 921 the Mal-gal tribe, Heuk-su, made a treaty with Wang-gön. This bears evidence to the rapidly growing power of the young king. The Heuk-su Mal-gal were the most feared of all the semi-savage tribes of the north. The following year the Kŭ-ran, usually called Kitan in Chinese histories, followed the example of the Heuk-su people by sending an envoy with presents. It was not till 923 that Wang-gön thought fit to send an envoy to China to offer his compliments. When the last king of Sil-la, but one, ascended the throne in 924 important events were following thick and fast upon each other. Sil-la was now so weak that the records say the king had nothing left but his genealogy. Kyŭn-whŭn sent a force to begin operations against Koryŭ, but without success, and in the following year Wang-gön retaliated with such good success that Kyŭn-whŭn was fain to send his son to Song-do as a hostage. He thus bound himself to keep the peace. Having done this he sent to China desiring to secure backing against Koryŭ. The Emperor so far complied as to confer upon him the title of King of Păk-je, thus following the time-honored policy of pitting one power against another.