It was now the year 1231, the year which saw the outbreak which had been threatening ever since Genghis Khan came to the chieftainship of the Mongol armies. As the spring opened a powerful Mongol army moved southward across the Yalu under the leadership of Sal Ye-t‘ap and took the fortress of Ham-sin near Eui-ju. They followed this up by storming Ch‘ŭl-ju which ended only after the prefect had set fire to his house and destroyed his whole family and he and his associates had cut their own throats.
The king did not intend to submit without a struggle. He sent Generals Pak Sö and Kim Kyöng-sol at the head of a large army to operate against the invaders. They rendezvoused with all their forces at Ku-ju, the four gates of which were strongly barricaded. The Mongols commenced the attack at the south gate. The Koryŭ soldiers made five brilliant sallies and forced the enemy to retire. The honors of this victory fell to Gen. Kim who pursued the enemy some distance and then returned to the town in triumph. The Mongols, who seem to have been independent of any base of supplies and made the country through which they passed supply them, now left this town untaken and the Koryŭ army undefeated in their rear, and marched boldly southward, taking Kwak-ju and Sŭn-ju. From this point the Mongol general Sal Ye-t‘ap sent a letter to the king saying “Let us make peace. We have now taken your country as far as Han-sin and if you do not come to terms with us we will draw reinforcements from Yŭ-jin and crush you.” The messenger who conveyed this very candid letter got only as far as P‘yŭng-ju where he was seized by the people and imprisoned. While waiting for an answer, the invaders tried another attack on Ku-ju but with no better success. Not only so, but they were badly defeated at Au-puk fortress.
The king now reinforced the army in the north and at the same time feasted 30,000 monks at the capital in order to influence the celestial powers to bring about a cessation of war. But at the same time the Mongol forces were reinforced by Yŭ-jin troops and with high spirits crossed the Ta-dong river and swept down to P‘yŭng-ju to wreak their vengeance on that place where even yet the Mongol messenger with the letter for the king was languishing in durance vile. By a night attack they took the place, burned it to the ground, killed the prefect and even destroyed every dog and other domestic animal in the place. Then they advanced toward Song-do and soon appeared beneath its walls. There the Mongol generals P‘o-do, Chŭk-kŭ and Tang-go went into camp. They supplied their army by foraging all through the surrounding country, in which operation thousands of people were killed, their houses destroyed and their goods confiscated, especially all kinds of food. The people in the capital were in the greatest distress. Ch‘oe U, the viceroy, stationed all the best troops about his own house and left the inferior troops to guard the palace.
The Mongol general Sal Ye-t‘ap was now in the north. The king had already sent one messenger to ask for terms of peace and had received the following answer; “I am emperor. If you wish to fight it out then come on and fight. If not then surrender, and be quick about it, too.” The king now sent another messenger on a similar errand. He returned with two Mongol commissioners and three more soon followed. They were immediately admitted to an audience and a conference followed, after which the king sent rich presents to Gen. Sal Ye-t‘ap who seems now to have joined the main army before Song-do, and also to the other generals. What the result of the conference was is, for some reason, not stated in the records, but that it was not entirely satisfactory to the Mongols, or if satisfactory not sufficiently so to make them forego the pleasure of plundering, is seen from their next move, for they left Song-do and went southward to the center of the peninsula, the rich province of Ch‘ung-ch‘ŭng.
The cowardly prime minister showed his colors by sending a man to find a retreat for him on the island of Kang-wha, but the messenger fell into the hands of Mongol foragers.
Gen. Sal Ye-t‘ap had gone north and joined another division of the Mongol army and again he attacked Ku-ju. He made engines of war called ta-p‘o-ch‘a, a sort of catapult, with which to reduce this town, but the magistrate, Pak Sö also made similar instruments which hurled huge stones, and the besiegers were compelled to retire to a distance and take refuge behind various kinds of defenses. The Mongols made three attempts to deceive the prefect by forged letters purporting to be from the king and saying “I have surrendered and therefore you must submit,” but Pak Sö was not to be caught by so simple a trick. The besiegers then tried huge scaling ladders, but these were cut down by the defenders as fast as they were put in place. An aged Mongol general, who made a circuit of the town and marked the splendid state of defense into which the place had been put, declared that he had never seen a place so well defended.
So the little town stood and the great Mongol general was forced to seek other fields for the display of his prowess. He sent a letter to the king finding fault because of the death of the first Mongol messenger[messenger] and modestly suggesting that peace could be secured if he would surrender and give 20,000 horse-loads of clothing, 10,000 pieces of purple silk, 20,000 sea-otter skins, 20,000 horses, 1,000 boys, 1,000 girls and 1,000,000 soldiers, with food, to help conquer Japan. In addition to this the king must go to the Mongol court and do obeisance. These were the terms upon which Koryŭ could secure peace.
With the beginning of the next year, 1232, the king sent two generals bearing a letter of surrender. With it he sent seventy pounds of gold, thirteen pounds of silver, 1,000 coats and a hundred and seventy horses. He moreover stated that the killing of the Mongol messenger was not the work of the Koryŭ government but of a band of insurgents and robbers. The officials had to give their garments in order to make up the number that was sent. Each prefect along the route was charged with the duty of seeing that the Mongols were in no way molested.
But Pak Sö the prefect of Ku-Ju[Ku-Ju] was an obstinate man and would not give up his fortress even when he knew the king had surrendered. It was only after a great deal of argument and expostulation that he at last capitulated. The Koryŭ people wanted to kill him for his obstinacy but the Mongols said “He is your greatest man and you should prize him highly.”
So ended the first act of the tragedy, but it was not to be the last. A Mongol residency was established at Song-do and Mongol governors were stationed at important centers throughout the country. The Mongol resident insisted upon entering the palace by the middle gate which the king alone used, but it was shut and barred and he was not able to carry his point. When the tribute above mentioned reached Gen. Sal Ye-t‘ap he expressed the greatest dissatisfaction with it because it fell so far short of what was demanded and he imprisoned the messenger who brought it. The king sent an envoy to the Mongol capital saluting the emperor as suzerain for the first time.