Kublai received this charge in 1251, so that the Sungs had enjoyed, first through the pacific disposition of Ogotai, and, secondly, from the family disputes following his death, peace for more than fifteen years. The advantage of this tranquillity was almost nullified by the death of Mongkong, a general whose reputation may have been easily gained, but who certainly enjoyed the confidence of his soldiers, and who was thought by his countrymen to be the best commander of his day. When the Chinese emperor, Litsong, saw the storm again approaching his northern frontier, he found that he had lost the main support of his power, and that his military resources were inferior to those of his enemy. He had allowed himself to be lulled into a false sense of security by the long inaction of the Mongols, and although he seems to have been an amiable prince, and a typical Chinese ruler, honoring the descendants of Confucius with the hereditary title of duke, which still remains in that family, and is the only title of its kind in China, and encouraging the literary classes of his country, he was a bad sovereign to be intrusted with the task of defending his realm and people against a bold and determined enemy. Kublai prepared the way for his campaigns in Southern China by following a very wise and moderate policy in Northern China similar to that begun by Muhula, and carried out with greater effect by Yeliu Chutsai. He had enjoyed the advantage of a Chinese education, imparted by an able tutor named Yaochu, who became the prince's private secretary and mentor in all Chinese matters. At his instigation, or, at least, with his co-operation, Kublai took in hand the restoration of the southern portion of Honan, which had been devastated during the wars, and he succeeded in bringing back its population and prosperity to that great province of Central China. He thus secured a base for his operations close to the Sung frontier, while he attached to his person a large section of the Chinese nation. There never was any concealment that this patronage of Chinese officials, and these measures for the amelioration of many millions of Chinese subjects, were the well calculated preliminaries to the invasion of Southern China and the extinction of the Sung dynasty.