[2] Using his rival Nilga Senggum's temporary refuge in Western Xia as a pretext, Temujin launched a raid against the state in 1205 in the Edsin region.

In 1207, Genghis led another raid into Western Xia, invading the Ordo region and sacking Wuhai, the main garrison along the Yellow River, before withdrawing in 1208.

[7] The Mongols were not yet experienced with siege warfare, and attempted to build a dike to divert the Yellow River and flood the city.

In 1219, Genghis Khan launched his campaign against the Khwarazmian dynasty in Central Asia, and requested military aid from Western Xia.

However, the emperor and his military commander Asha refused to take part in the campaign, stating that if Genghis had too few troops to attack Khwarazm, then he had no claim to supreme power.

[9][10] Infuriated, Genghis swore vengeance and left to invade Khwarazm, while Western Xia attempted alliances with the Jin and Song dynasties against the Mongols.

[11] After defeating Khwarazm in 1221, Genghis prepared his armies to punish Western Xia for their betrayal, and in 1225 he attacked with a force of approximately 180,000.

[13] Enraged by Western Xia's fierce resistance, Genghis engaged the countryside in annihilative warfare and ordered his generals to systematically destroy cities and garrisons as they went.

[15] In August 1226, Mongol troops approached Wuwei, the second-largest city of the Western Xia empire, which surrendered without resistance in order to escape destruction.

[16] In Autumn 1226, Genghis took Liangchow, crossed the Helan Shan desert, and in November lay siege to Lingwu, a mere 30 kilometers from Yinchuan.

In his typically logical and determined fashion, Genghis and his highly developed staff studied the problems of the assault of fortifications.

As a result of a number of overwhelming victories in the field and a few successes in the capture of fortifications deep within China, Genghis had conquered and consolidated Jin territory as far south as the Great Wall by 1213.

Han Chinese defectors led by General Liu Bolin defending Tiancheng from the Jin in 1214 while Genghis Khan was busy going back north.

[40][41][42][43] Shi Tianze (Shih T'ien-tse), Zhang Rou [zh] (Chang Jou, 張柔), and Yan Shi [zh] (Yen Shih, 嚴實) and other high ranking Chinese who served in the Jin dynasty and defected to the Mongols helped build the structure for the administration of the new state.

A new infantry based "New Army" (Xin Jun) was created after the Mongols received 95,000 additional Han soldiers through conscription once the 1236 and 1241 censuses were taken after the Jin was crushed.

[50] The Mongols valued physicians, craftsmen and religious clerics and ordered them to be spared from death and brought to them when cities were taken in northern China.

The Dali King Duan Xingzhi [zh] (段興智) himself defected to the Mongols, who used his troops to conquer the rest of Yunnan.

[55] 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.

[59] While the Mongol forces had success against the non-Han Chinese ruled states of the Jin and Xia, conquering the Song took much more time.

The Song forces were equipped with the best technology available at the time, such as an ample supply of gunpowder weapons like fire lances, rockets and flamethrowers.

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

[65] Chagaan (Tsagaan) and Han tumen General Zhang Rou jointly launched an attack on the Song dynasty ordered by Töregene Khatun.

After several indecisive wars, the Mongols unsuccessfully attacked the Song garrison at Diaoyu Fortress, Hechuan, when their Great Khan, Möngke, died of cholera or dysentery.

After a siege that lasted several years, and with the help of Muslim artillery created by Iraqi engineers, the Mongols finally forced the city of Xiangyang to surrender.

[69] According to Japanese historian Sugiyama Masaaki (杉山正明) and Funada Yoshiyuki (舩田善之), there were also a certain number of Mongolian slaves owned by Han Chinese during the Yuan dynasty.

The ancestors of the Tran clan originated from the modern day province of Fujian as did the Daoist cleric Xu Zongdao who recorded the Mongol invasion and referred to them as "Northern bandits".

Southern Song Chinese military officers and civilian officials left to overseas countries, went to Vietnam and intermarried with the Vietnamese ruling elite and went to Champa to serve the government there as recorded by Zheng Sixiao.

[87] Southern Song soldiers were part of the Vietnamese army prepared by emperor Trần Thánh Tông against the second Mongol invasion.

[124] "Mangu enlisted in his bodyguard half the troops of the Alan prince, Arslan, whose younger son Nicholas took a part in the expedition of the Mongols against Karajang (Yunnan).

[131] 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.