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.
The year 926 saw the first envoy come from the kingdom of T‘am-na on the island of Quelpart. He arrived at the capital of Koryŭ, where he was well received. The fame of Wang-gön was spreading far and wide among the northern tribes. The Kŭ-ran, or Kitan tribe, having overcome the Păl-ha tribe, made overtures to Wang-gön relative to annexation. These advances were cordially responded to but we are not informed that the union was actually effected.
Kyŭn-whŭn, who was at this time on the island Chŭl-yong-do, sent a present of horses to Wang-gön but a few days later he found a book of prophecy which said that in the year when he should send a gift of horses to Song-do his power would come to an end. He therefore sent a swift messenger begging Wang-gön to return the gift. The King laughed long and loud when he saw this message and good-naturedly sent back the horses.
The last King of Sil-la, Kyŭng-sun, ascended the throne in 927. It happened on this wise; Kyŭn-whŭn was keeping up a double fight, one against Wang-gön and the other, an offensive one, against Sil-la. He was badly defeated in an engagement with Koryŭ forces but had good success in his other venture. He burned and pillaged right up to the gates of Sil-la’s capital, and, while a Sil-la envoy was posting to Song-do to ask for aid, entered the city with a picked band of men. Succor in the shape of 10,000 Koryŭ troops was on its way but came too late. At the hour when Kyŭn-whŭn entered the city the king, his son, the queen and many of the courtiers were feasting at Po-sŭk summer-house. When the unwelcome news arrived, there was no time for preparation. The king and queen fled south without attendants. The palace women were seized and the palace occupied. The king was soon run to earth and was compelled to commit suicide. Kyŭn-whŭn ravished the queen and delivered over the palace women to the soldiery. The palace was looted and the entire band, sated with excess and debauchery, and loaded down with the treasures of the palace, started back on the homeward road. But not until Kyŭn-whŭn had appointed a relative of the murdered king to succeed him.