In 1234, the first year of Emperor Lizong’s reign in the Song Dynasty, the Southern Song Dynasty and Mongolian armies joined forces to conquer Caizhou, the last residence of the Jin emperor. The Jin Kingdom, which rose from the white mountains and black waters and occupied the Central Plains for more than a hundred years, perished.
Soon, the Southern Song Dynasty and Mongolia, who had lost their country and the enemy, met each other in war. In 1235, Wokuotai sent two troops south to attack the Southern Song Dynasty on the grounds that the Song Dynasty had violated the alliance. The prince Kuo Chu led the army to attack the Jingxiang area, and the prince Kuo Duan led the army to attack Sichuan. Under the continuous attacks of the Mongolian army, the Song army was forced to make a strategic retreat.
Zong Lizong of the Song Dynasty ordered the Lianghuai, Yanjiang, and Jinghu Production Departments to organize farming in Jiangbei and Huaixi, set up Baojia, and set up guerrilla armies in the Lianghuai and Yanjiang areas. Under the leadership of the famous generals Meng Gong and Yu Jie, they relied on rivers, mountains and other terrains that were not conducive to the galloping of war horses to build castles and stockades for defense. At the same time, they dug trenches in areas close to the border to establish a deep defense system.
Until Wo Kuotai's death in 1241, the Mongolian army was never able to form an absolute military advantage over the Southern Song Dynasty. Even Kuo Chu, Wo Kuotai's favorite son, died in the war against the Song Dynasty. After that, both Mongolia and the Southern Song Dynasty had their own gains and losses in the border offensive and defensive battles. The eastern front was along the Huaihe River, the middle line was stable in the Dabie Mountains, and the western front was in northern and western Sichuan. The stalemate lasted for nearly 20 years.
In 1251, Meng Ge from the Tolei family succeeded to the throne and became the fourth Great Khan of the Mongolian Empire. A month later, he appointed his younger brother, Kublai Khan, to take charge of the military affairs of Monan Han. Monan is the south of the Gobi Desert. It generally refers to the Han Dynasty in the Central Plains that was captured from the Jin Kingdom. There is no say as to where south it goes. Mongolians have lived in vast grasslands since childhood and have always had a broad vision. The fiefdom Genghis Khan gave his eldest son Jochi was west of the Irtysh River. Wherever the Mongolian horse's hooves hit, it meant wherever it could hit.
Kublai Khan was appointed as Prime Minister of the Monan Han Dynasty to be in charge of the military. His first task was to continue preparing for the military conquest of the Southern Song Dynasty. Beginning in 1234, Mongolia had launched a continuous war against the Southern Song Dynasty for more than ten years. They successively appointed three great khans, Ogedai, Guyu and Mengge, but they never made much progress. This made the first-time Khan Brother Meng was very depressed.
He said, "My father and brothers, the great khans in the past, each have established achievements, conquered a certain area, and improved their reputation." ?He appointed another brother, Hulagu, to launch an expedition against Persia, and at the same time ordered Kublai Khan to actively prepare for an attack on the Southern Song Dynasty.
Yao Shu, a Han adviser to Kublai Khan, analyzed the various mistakes made by the Mongolian army since 1235 and pointed out that in the past years of battles, "generals were killed for profit and all the treasures of their children were returned to their homes". They plundered all the people and turned them into private slaves. This not only caused the people of the Southern Song Dynasty to resist to the death, but also led to the land where there were no residents in the city and the wild areas were wild. The military results could not be consolidated at all. This was by no means a strategy to stabilize the country.
He suggested that Kublai Khan should change the military operations of spring and autumn, focusing on plundering, into the long-term war preparations of dividing key areas, focusing on defense, and also fighting and plowing, and cultivate the areas at the junction of Mongolia and Song Dynasty. Guard the border and wait until the border preparations are sufficient before you can do anything big.
Kublai felt that what Yao Shu said was very reasonable, so he stationed heavy troops in the area starting from Rangdeng (now Dengzhou, Henan) in the west, forming a horn with Xiangyang (now Xiangyang, Hubei), heading east Connecting Chenzhou (now Huaiyang County, Henan), Bozhou (now Bozhou, Anhui), Qingkou, and Taoyuan (now Siyang, Jiangsu), it formed a defensive barrier and waited for opportunities to attack the Southern Song Dynasty.
In order to solve the logistical supply problem of this defense line, he set up a transshipment department in Weizhou (now Weihui, Henan) to transport grain to the Huaihe front line through the Yellow River.
But facing the thousands-mile front line stretching from Jianghuai in the east to Sichuan in the west, the Mongolian army's biggest weakness is that they are not used to water warfare, and they urgently need to find new breakthroughs. Kublai Khan set his sights on Dali, a small country in the remote southwest. Dali was a vassal state of the Southern Song Dynasty. The king was once awarded the title of Yunnan Jiedushi, Dali King and other official titles. Dali is not only rich in food but also produces fine horses. It is the main source of war horses in the Southern Song Dynasty. Occupying Dali can form a greater advantage over the Southern Song Dynasty in cavalry.
More importantly, under the stubborn defense of the Southern Song Dynasty, occupying Dali allowed the Mongolian army to bypass the weakly defended Guangdong and Guangxi areas of the Southern Song Dynasty, and then return to the north to outflank and attack the middle and lower reaches of the Yangtze River from the southwest. In Mongolian, it is called "bouti". During the hunting process, the prey must be hunted by surrounding it on all sides. They also used this encirclement tactic during combat, and when hunting ferocious animals, they often had to attack their soft abdomen, which was more effective.
So Kublai Khan went to Hara and Linjin to see Meng Ge and asked for permission to conquer Dali first, so as to form a siege on the Southern Song Dynasty from the side and destroy the Song Dynasty in one fell swoop.
The territory of the Dali Kingdom covered today's Yunnan, Guizhou, southwestern Sichuan, western Guangxi, and parts of Myanmar, Laos, and northern Vietnam. Its predecessor was the Nanzhao Kingdom established during the Xuanzong period of the Tang Dynasty. During the late Tang Dynasty and the Five Dynasties period, Nanzhao fell into chaos. Duan Siping, who was born a nobleman of the Bai ethnic group, established the Dali Kingdom twenty-three years before Zhao Kuangyin and Chen Qiao rebelled and became Huangpao. After Zhao Kuangyin wore the yellow robe, he announced that "I don't own anything outside the Dadu River", and the Dali Kingdom continued to exist.
In 1244, the Mongolian Khan Guiyu ordered the Mongolian army participating in the conquest of Shu to mobilize elite troops in an attempt to capture Dali.
King Duan Xiangxing of Dali fought fiercely with the Mongolian army in the Jiuhe area of ??Lijiang, but the Mongolian army finally returned without success.
In the winter of 1248, the Mongolian general Tulu once again led his army to attack Yanzhou (now north of Luding County) on the west bank of the Dadu River, trying to find a way south from the Qiang tribe to attack Dali. Sichuan made Yu Jie was well aware that the Mongolian army's strategic detour was disadvantageous to the Song army, so he sent two groups of Song troops to march westward, crossing the country's border and crossing the Snowy Mountains to intercept the Mongolian army front and rear. At the same time, Yang Wen (1248), the pacification envoy of Bozhou (now Zunyi, Guizhou), led three thousand infantry and cavalry, and came out of the snowy mountains from Diaomen (north of Tianquan County, Sichuan). The Song army won three battles and captured the Mongolians on the banks of the Dadu River. The commander of the army was bald.