With the end of Queen Söng-man’s reign affairs in the peninsula began to focus toward that crisis which Ko-gu-ryŭ and Păk-je had so long been preparing for themselves. In 655 a new combination was effected and one that would have made Sil-la’s horizon very dark had she not been sure of Imperial help. Her two neighbors formed a league against her, and of course the Mal-gal tribes sided with Ko-gu-ryŭ in this new venture. Păk-je and Ko-gu-ryŭ were drawn together by their mutual fear of Sil-la and soon the allied armies were marching on Sil-la’s borders. At the first onslaught thirty-three of Sil-la’s border forts passed into the hands of the allies. It was now China’s last chance to give aid to the most faithful of her Korean vassals, for otherwise she would surely have fallen before this combination. A swift messenger was sent imploring the Emperor for aid and stating that if it was not granted Sil-la would be swallowed up. The Emperor had no intention of letting Sil-la be dismembered and without a day’s delay troops were despatched into Liao-tung under Generals Chŭng Myŭng-jin and So Chöng-bang. Many of Ko-gu-ryŭ’s fortresses beyond the Yalu River were soon in the possession of China. This was successful in diverting Ko-gu-ryŭ’s attention from Sil-la, but Păk-je continued the fight with her. The advantage lay now with one side and now with the other. The court of Păk-je was utterly corrupt and except for a small army in the field under almost irresponsible leadership, she was weak indeed.
Now it happened that a Sil-la man named Cho Mi-gon had been taken captive and carried to Păk-je where he was employed in the household of the Prime Minister. One day he made his escape and found his way across the border into his native country, but there meeting one of the Sil-la generals he was induced to go back and see what he could do in the Păk-je capital towards facilitating an invasion on the part of his countrymen. He returned and after sounding the Prime Minister found him ready to sell his country if there was anything to be made out of it. It is said that here began the downfall of Păk-je. The king of Păk-je was utterly incompetent and corrupt. One of his best councillors was thrown into prison and starved to death for rebuking him of his excesses. But even while this faithful man was dying he sent a message to the king saying “Do not fail to place a strong garrison at ‘Charcoal Pass’ and at Păk River.” These were the two strategic points of Păk-je’s defenses; if they were guarded well, surprise was impossible. From that time affairs in Păk-je went from bad to worse. China kept Ko-gu-ryŭ busy in the north and nothing of consequence was gained by either side in the south until finally in 659 another Sil-la envoy made his appearance in the Emperor’s court. At last the great desire of Sil-la was accomplished. The Emperor ordered Gen. So Chöng-bang to take 130,000 men by boat to the shores of Păk-je and there coöperate with a Sil-la army in the utter subjugation of Păk-je. The Sil-la army went into camp at Nam-ch’ŭn and received word from the Chinese general to meet him at the Păk-je capital in the seventh moon.