In 1251 AD, his eldest brother Meng Ge became the Great Khan. As a relative of the emperor's brother, Kublai Khan was appointed as the Prime Minister of the Monan Han Dynasty, military affairs and common affairs, and was stationed in the south of Hudu.

After Meng Ge came to the throne, he sent Kublai Khan to open up the southern Han Dynasty, ordered Hulagu to expedition to the Western Regions, and left Alibuge to stay in Helin to look after the Mongolian mainland, while he personally led an army to attack the Song Dynasty.

The Song-Mongolian (Yuan) War broke out in full force in 1235 AD and ended with the fall of the Song Dynasty at the Battle of Yashan in 1279. It lasted for nearly half a century. It was the longest and most time-consuming war that the Mongolian power had encountered since its rise. The most labor-intensive and difficult war. The Battle of Diaoyu City in Hezhou, Sichuan in 1259 was one of the most influential battles.

After the Song and Mongolia jointly destroyed the Jin Dynasty in 1234, the Southern Song Dynasty sent troops to regain the lost land in Henan, but was ambushed by the Mongolian army and failed. In 1235, the Mongolian army simultaneously launched an attack on the Southern Song Dynasty on a front line spanning thousands of miles from Sichuan and Shaanxi in the west to the lower reaches of the Huaihe River in the east. The Song-Mongolian War broke out in an all-round way. By 1241, the Mongolian cavalry ravaged a large area of ??land in the Southern Song Dynasty, and Sichuan was the most severely damaged by the Mongolian army among the three major battlefields (the other two were the Jinghu Battlefield, which is now Hubei and Henan, and the Lianghuai Battlefield, which is now the Huaihe River Basin) area.

Mongolian Ogedai died in this year, and its internal political disputes continued, and its offensive against the Southern Song Dynasty weakened. This gave the Southern Song Dynasty a chance to breathe and adjust and enrich the defenses on various battlefields. In 1242, Emperor Lizong of the Song Dynasty sent Yu Jie, who had achieved great results in the Huaihe-Huaihe War against Mongolia, to take charge of Shu to reverse Sichuan's decline and consolidate the upper class. Yu Jie took a series of political, economic and military measures in Sichuan, the most important of which was the creation of a mountain city defense system. That is, along the main rivers and transportation thoroughfares in Sichuan, precipitous mountain passes were selected to build fortifications and fortifications. They were dotted and supported each other, forming a complete strategic defense system. Diaoyu City is the core and strongest fortress of this mountain city defense system.

Diaoyu City is located on Diaoyu Mountain, 5 kilometers east of present-day Hechuan County, Sichuan Province. The mountain stands abruptly, with a relative height of about 300 meters. At the foot of the mountain, the Jialing River, Qujiang River and Fujiang River converge. It is surrounded by water on three sides to the south, north and west. The terrain is very dangerous. There are dangerous mountains and rivers here, but also convenient transportation. All parts of Sichuan can be reached by water and land. When Peng Daya served as deputy envoy of Sichuan Province (1239-1240), he ordered Gan Runchu to build Diaoyu City. In 1243, Yu He adopted the advice of brothers Ran He and Ran Pu, sages from Bozhou (now Zunyi), and sent the Ran brothers to rebuild Diaoyu City and transfer the governorship of Hezhou and Xingyuan to it. The fishing city is divided into an inner city and an outer city. The outer city is built on a cliff, and the city wall is made of stone. There are large fields and abundant water sources in the city all year round, and there are also many arable fields in the surrounding foothills. All these make Diaoyu City have the necessary geographical conditions for long-term persistence and the characteristics of relying on natural dangers, easy to defend and difficult to attack. In 1254, Hezhou defender Wang Jian further improved the city construction. Many people from the border areas of Sichuan came here to avoid military chaos, and Diaoyu City became a strong fortress where soldiers were well fed.

In 1251, Meng Ge ascended to the throne of the Great Khan, stabilized the political situation of Mongolia, and actively planned the war to destroy the Song Dynasty. Meng Ge was the eldest son of Genghis Khan's youngest son Tuo Lei. He led troops with Batu and others on expeditions to many countries in Europe and Asia, and was known for his bravery and skill in warfare. In 1252, Mengge Khan ordered his younger brother Kublai Khan to lead an army to capture Dali, forming an encirclement and pincer attack on the Southern Song Dynasty.

In 1257, Mengge Khan decided to launch a large-scale war to destroy the Song Dynasty. Meng Ge ordered Kublai Khan to lead his army to attack Ezhou (today's Wuchang), Tacha'er, Li Yu and others to attack the Huaihe River and divide the Song forces. He also ordered Wu Lianghetai to send troops from Yunnan and go northward via Guangxi; Meng Ge led the Mongolian army himself. The main force of the army attacked Sichuan. Meng Ge took Sichuan as the main strategic direction of attack, intending to take advantage of the Mongolian cavalry's characteristics of being good at land battles but poor at water battles, seize Sichuan with the main force, then go eastward along the river, join forces with other roads, and march directly to Lin'an (now Hangzhou), the capital of the Song Dynasty.

In the autumn of 1258, Meng Ge led an army of 40,000 into Shu in three groups. Adding the Mongolian troops in Shu and troops recruited from various places, the total number of Mongolian troops greatly exceeded 40,000. The Mongolian army successively occupied Jianmen Kuzhu Pass, Changning Mountain City, Pengzhou Yunshan City, Langzhou Dahuo City, Guang'an Daliang City, etc., approaching Hezhou.

Meng Ge Khan sent Song's surrender Jin Guobao to Diaoyu City to recruit surrender, but he was killed by Wang Jian, the defender of Hezhou in Song. The Battle of Diaoyu City begins.

On February 2, the first year of Kaiqing's reign in the Song Dynasty (1259), Meng Ge led his troops across the Quhui from Jizhatan and camped at Shizi Mountain. On the third day, Meng Ge personally supervised the troops fighting at the foot of Diaoyu City. On the seventh day, the Mongolian army attacked the Yizi city wall. The one-character city wall is also called the horizontal city wall. Its function is to hinder the movement of enemy troops outside the city. At the same time, the defenders in the city can move through the outer city wall to the one-character city wall to resist the enemy, forming an angled cross attack point with the outer city wall. There is a one-character city wall built in the south and north of Diaoyu City. On the 9th, the Mongolian army stormed the west gate of the town, but failed. On this day, the Mongolian host army Shi Tianze and his troops also arrived at Diaoyu City to join the battle.