All this time fighting was almost continuous along the Ko-gu-ryŭ-Păk-je border. The latter stood on the defensive and found it necessary in 386 to build a line of breastworks along the border, extending from Ch’ŭng-mok-yŭng northward to P’al-gon-sung and thence westward to the sea. An amnesty was brought about through a happy accident. A groom who had accidentally broken the leg of a Păk-je prince’s horse had fled to Ko-gu-ryŭ to escape punishment. Returning now to Păk-je, he purchased pardon by informing the king that if, in battle, the Păk-je forces should direct their whole force against that part of the enemy’s line where they should see a red flag flying they would surely be successful. This turned out to be true and Păk-je was once more successful, but followed up her success only to the extent of securing a definite cessation of hostilities and the erection of a boundary stone at Su-gok-sŭng to witness forever against him who should dispute the point. But when King Ch’im-yu of Ko-gu-ryŭ died in 392 and his son Tam-dok came into power all previous obligations were swept away and he proceeded to reopen the wound. He attacked Păk-je fiercely and took ten of her towns. Then he turned northward and chastised the Kŭ-ran tribe. When this was done he came back to the charge again and seized Kwang-nu Fortress. This was an almost inaccessible position on a high rock surrounded by the sea, but the hardy soldiers of Ko-gu-ryŭ after twenty days of siege found seven paths by which the wall could be reached, and they finally took the place by a simultaneous assault at these various points. When the court of Păk-je heard of this well-nigh impossible feat, all hope of victory in the field was taken away, and they could only bar the gates of the capital and await the turn of events. This king, Tam-dok, was as enthusiastically Buddhistic as his father. He made a decree that all the people of Ko-gu-ryŭ should adopt the Buddhistic faith and a few years later built nine more monasteries in P’yŭng-yang.
A year later King A-sin of Păk-je sent his son, Chön-ji, to Japan as an envoy. It is likely, but not certain, that it was a last resource of Păk-je to secure help against Ko-gu-ryŭ. This is the more likely from the fact that he went not only as an envoy but also as a hostage, or a guarantee of good faith. If this was the hope of Păk-je it failed, for no Japanese army was forthcoming. As another means of self-preservation King A-sin formed a great school of archery, but the people did not like it; for exercise in it was compulsory, and many of the people ran away.