Gen. Ko-gan hastened forward and engaged the Ko-gu-ryŭ forces at Keum-san and won a decided victory, while at the same time Gen. Sŭl-In gwi was reducing the fortresses of Nam-so, Mok-jŭ and Ch‘ang-am, after which he was joined by the Mal-gal forces under the renegade Nam-săng. Another Chinese general, Wŭn Man-gyŭng, now sent a boastful letter to the Ko-gu-ryŭ capital saying “Look out now for the defenses of that precious Am-nok River of yours.” The answer came grimly back “We will do so.” And they did it so well that not a Chinese soldier set foot on the hither side during that year. The Emperor was enraged at this seeming incompetence and banished the boastful general to Yong-nam. A message had already been sent to Sil-la ordering her to throw her army into Ko-gu-ryŭ and for the Chinese generals Yu In-wŭn and Kim In-t‘ă to meet them before P‘yŭng-yang. These two generals were in Păk-je at the time.
In 668 everything beyond the Yalu had fallen into the hands of the Chinese; even Pu-yŭ Fortress of ancient fame had been taken by Gen. Sŭl In-gwi. The Emperor sent a messenger asking “Can you take Ko-gu-ryŭ?” The answer went back “Yes, we must take her. Prophecy says that after 700 years Ko-gu-ryŭ shall fall and that _eighty_ shall cause her overthrow. The 700 years have passed and now Gen. Yi Jök is eighty years old. He shall be the one to fulfill the prophecy.”
Terrible omens had been seen in the Ko-gu-ryŭ capital. Earthquakes had been felt; foxes had been seen running through the streets; the people were in a state of panic. The end of Ko-gu-ryŭ was manifestly near. So tradition says.
Nam-gŭn had sent 50,000 troops to succor Pu-yŭ Fortress but in the battle which ensued 30,000 of these were killed and the remainder were scattered. Conformably to China’s demands, Sil-la in the sixth moon threw her army into Ko-gu-ryŭ. The great Sil-la general, Kim Yu-sin was ill, and so Gen. Kim In-mun was in command with twenty-eight generals under him. While this army was making its way northward the Chinese under Gen. Yi Jök in the north took Tă-hăng Fortress and focussed all the troops in his command upon the defenses of the Yalu. These defenses were broken through, the river was crossed and the Chinese advanced 210 _li_ toward the capital without opposition. One by one the Ko-gu-ryŭ forts surrendered and at last Gen. Kye-p‘il Ha-ryŭk arrived before the historic city of P‘yŭng-yang. Gen. Yi Jök arrived next and finally Gen. Kim In-mun appeared at the head of the Sil-la army.