It was at this time, 671, that the term Il-bün (Nippon) was first used in Korea in connection with the kingdom of Japan.
The relations between Sil-la and Păk-je were badly strained. In the following year the Chinese threw a powerful army into Păk-je with the evident intention of opposing Sil-la. So the latter furbished up her arms and went into the fray. In the great battle which ensued at the fortress of Sŭk-sŭng 5,000 of the Chinese were killed. Sil-la was rather frightened at her own success and when she was called upon to explain her hostile attitude toward China she averred that it was all a mistake and she did not intend to give up her allegience to China. This smoothed the matter over for the time being, but when, a little later, the Emperor sent seventy boat loads of rice for the garrison at P‘yŭng-yang, Sil-la seized the rice and drowned the crew’s of the boats, thus storing up wrath against herself. The next year she attacked the fortress of Ko-sŭng in Păk-je and 30,000 Chinese advanced to the support of the Păk-je forces. A collision took place between them and the Sil-la army in which the Chinese were very severely handled. This made the Emperor seriously consider the question of subduing Sil-la once for all. He ordered that the Mal-gal people be summoned to a joint invasion of the insolent Sil-la and the result was that seven Sil-la generals were driven back in turn and 2,000 troops made prisoners. In this predicament there was nothing for the king to do but play the humble suppliant again. The letter to the Emperor praying for pardon was written by the celebrated scholar Im Gang-su. But it was not successful, for we find that in the following year the Chinese troops in the north joined with the Mal-gal and Kŭ-ran tribes in making reprisals on Sil-la territory. This time however Sil-la was on the alert and drove the enemy back with great loss. She also sent a hundred war boats up the western coast to look after her interests in the north. At the same time she offered amnesty and official positions to Păk-je nobles who should come over to her side.
We can scarcely escape the conviction that Sil-la had now become a military power of no mean dimensions. Many citizens of Ko-gu-ryŭ had come over to her and some of the Păk-je element that was disaffected toward the Chinese. All, in fact, who wanted to keep Korea for the Koreans and could put aside small prejudices and jealousies, gathered under the Sil-la banners as being the last chance of saving the peninsula from the octopus grasp of China. Sil-la was willing to be good friends with China—on her own terms; namely that China should let her have her own way in the peninsula, and that it should not be overrun by officious generals who considered themselves superior to the king of the land and so brought him into contempt among the people.