When Utubu saw the Mongols retreating, he thought to provide against the most serious consequences of their return by removing his capital to a greater distance from the frontier, and with this object he transferred his residence to Kaifong. The majority of his advisers were against this change, as a retirement could not but shake public confidence. It had another consequence, which they may not have contemplated, and that was its providing Genghis with an excuse for renewing his attack on China. The Mongol at once complained that the action of the Kin emperor implied an unwarrantable suspicion of his intentions, and he sent his army across the frontier to recommence his humiliation. On this occasion a Kin general deserted to them, and thenceforward large bodies of the Chinese of the north attached themselves to the Mongols, who were steadily acquiring a unique reputation for power as well as military prowess. The great event of this war was the siege of Yenking--on the site of which now stands the capital Pekin--the defense of which had been intrusted to the Prince Imperial; but Utubu, more anxious for his son's safety than the interests of the state, ordered him to return to Kaifong. The governor of Yenking offered a stout resistance to the Mongols, and when he found that he could not hold out, he retired to the temple of the city and poisoned himself. His last act was to write a letter to Utubu begging him to listen no more to the pernicious advice of the man who had induced him to murder Hushahu.