The night was dark, and they succeeded in leaving the city without being observed. In the morning, however, all was discovered, and Genghis Khan sent off a strong detachment of well-mounted troops in pursuit. These troops, after about a day's chase, overtook the flying garrison near the river. There was no escape for the poor fugitives, and the merciless Monguls destroyed them almost every one by riding over them, trampling them down with their horses' hoofs, and cutting them to pieces with their sabres. In the mean time, while this detachment had been pursuing the garrison, Genghis Khan, knowing that there were no longer any troops within the city to defend it, and that every thing there was in utter confusion, determined on a grand final assault; but, while his men were getting the engines ready to batter down the walls, a procession, consisting of all the magistrates and clergy, and a great mass of the principal citizens, came forth from one of the gates, bearing with them the keys of the city. These keys they offered to Genghis Khan in token of surrender, and begged him to spare their lives. The emperor received the keys, and said to the citizens that he would spare their lives on condition that, if there were any of the sultan's soldiers concealed in the city, they would give them up, and that they would also seize and deliver to him any of the citizens that were suspected of being in the sultan's interest. This they took a solemn oath that they would do. The soldiers, however--that is, those that remained in the town--were not delivered up. Most of them retired to the castle, which was a sort of citadel, and put themselves under the command of the governor of the castle, who, being a very energetic and resolute man, declared that he never would surrender. There were a great many of the young men of the town, sons of the leading citizens, who also retired to the castle, determined not to yield to the conqueror. Genghis Khan, having thus obtained the keys of the city itself, caused the gates to be opened, and his troops marched in and took possession. He had promised the citizens that his soldiers should spare the lives of the people and should not pillage the houses on condition that the magistrates delivered up peaceably the public magazines of grain and other food to supply his army; also that all the people who had buried or otherwise concealed gold and silver, or other treasures, should bring them forth again and give them up, or else make known where they were concealed. This the people promised that they would do. After having entered the town, Genghis Khan was riding about the streets on horseback at the head of his troop of guards when he came to a large and very beautiful edifice. The doors were wide, and he drove his horse directly in. His troops, and the other soldiers who were there, followed him in. There were also with him some of the magistrates of the town, who were accompanying him in his progress about the city.