While Genghis Khan refused during his life, upon his death in 1227 he bequeathed a plan to attack the Jin capital by passing through Song territory.

In the early spring of 1227, Genghis Khan ordered a small fraction of the army to advance into the Song Lizhou Circuit, in the name of attacking Jin and Western Xia.

They advanced as far as Kaifeng but were completely repelled by the Mongol garrisons under Tachir, a descendant of Bo'orchu, who was a famed companion of Genghis Khan.

Mongol forces, headed by Genghis's son Ögedei Khan, began a slow, steady invasion of the south.

[19] An account of the Mongol attack on Nanjing was given in a Chinese annal, describing the Chinese defenders' use of gunpowder against the Mongols: As the Mongols had dug themselves pits under the earth where they were sheltered from missiles, we decided to bind with iron the machines called zhen tian lei [thunder-shaking-the-sky]... and lowered them into the places[20] where the translation of the term for the device is that of Prof. Partington, who describes it as an iron pot filled with [huo] yao, literally "fire drug", a low-nitrate gunpowder or proto-gunpowder, sometimes lowered on chains, that sent forth "fire... out of every part", with an incendiary effect over many yards that could pierce metal to which it was attached, producing a "noise like thunder" that could be heard for miles, with the result that "the men and the oxhides were all broken into fragments (chieh sui) flying in all directions".

Uriyangkhadai led successful campaigns in the southwest of China and pacified tribes in Tibet before turning east towards Dai Viet by 1257.

[23] In the autumn of 1257, Uriyangkhadai addressed three letters to Dai Viet emperor Trần Thái Tông demanding passage through southern China.

[27] While conducting the war in China at Diaoyu Fortress in modern-day Chongqing, Möngke died, perhaps of dysentery[28] or cholera, near the site of the siege on 11 August 1259.

[29][30][31] The central government of the Southern Song meanwhile was unable to cope with the challenge of the Mongols and new peasant uprisings in the region of modern Fujian led by Yan Mengbiao and Hunan.

The court of Emperor Lizong was dominated by consort clans, Yan and Jia, and the eunuchs Dong Songchen and Lu Yunsheng.

[citation needed] In 1260, Jia Sidao became chancellor who took control over the new emperor Zhao Qi (posthumous title Song Duzong) and expelled his opponents like Wen Tianxiang and Li Fu.

[citation needed] Gunpowder weapons like the tuhuo gun (突火槍), which fired bullets from bamboo tubes, were deployed by the Chinese against the Mongol forces.

[32] The Tusi chieftains and local tribe leaders and kingdoms in Yunnan, Guizhou and Sichuan submitted to Yuan rule and were allowed to keep their titles.

[38] As prizes for battlefield victories, lands sectioned off as appanages were handed by the Yuan dynasty to Chinese military officers who defected to the Mongol side.

[39] In 1268, the Mongol advance was halted at the city of Xiangyang, situated on the Han River, which controlled access to the Yangtze, the gateway to the important trading centre of Hangzhou.

The main entrances in the wall led out to a waterway impossible to ford in the summer, and impassable as a swamp and a series of ponds and mud flats in the winter.

[41] According to Professor Zhang Lianggao of Huazhong University of Science and Technology, in 1269 (咸淳五年), the Mongols invaded the Yangtze River valley but were repulsed.

Ismail and Al-aud-Din, from Mosul, Iraq, arrived in South China to construct a new type of counterweight-driven trebuchet that could use explosive shells.

According to the Ilkhanate historian Rashid Al-Din, the introduction of these weapons in 1268 was decisive and allowed the Mongols to rapidly conquer fortified cities they had previously deemed untakeable.

[45][46] Explosive shells had been in use in China for centuries, but the counterweight system of the trebuchet (as opposed to the torsion-type) gave greater range and accuracy while also making it easier to judge the force generated (versus by the torsion from repeated windings).

The effects of these shells on men and natural materials was devastating; the noise was thunderous and resounded for many miles, while the bomb's casing could penetrate iron armor during the explosion.

[citation needed] Political infighting in the Song also contributed to the fall of Xiangyang and Fancheng, due to the power of the Lü family.

Historian Patricia Buckley Ebrey notes that the Mongol Yuan dynasty treated the Jurchen Wanyan royal family harshly, butchering them by the hundreds as well as the Tangut emperor of Western Xia when they defeated him earlier.

Zhao Shi was enthroned as Emperor Duanzong of Song far from the capital in the region of Fuzhou, but he died soon afterwards on the flight southwards into modern Guangdong.

After the battle, as a last defiant act against the invaders, Lu Xiufu embraced the eight-year-old emperor and the pair leapt to their deaths from Mount Ya, thus marking the extinction of the Southern Song.

In February 1279, Wen Tianxiang, one of the Song loyalists, was captured, transported to and executed at the Yuan capital Khanbaliq (Dadu, modern Beijing).

Weather favored the Mongols that morning; heavy fog and rain obscured the approach of Li Heng's dawn attack.

The victory of this naval campaign marked the completion of Kublai's conquest of China, and the onset of the consolidated Mongol Yuan dynasty.

[citation needed] The Vietnamese Annals recorded that remnants of the Song imperial family arrived in Thăng Long, the capital of the Đại Việt, in the winter of 1276 aboard thirty ships and eventually settled in the Nhai-Tuân district and opened a market selling medicine and silk.

[64] The Khitan reluctantly left their homeland in Manchuria as the Jin moved their primary capital from Beijing south to Kaifeng and defected to the Mongols.