History of the Yuan dynasty - Wikipedia

On December 18, 1271, Kublai Khan renamed his empire "Yuan" (元 yuán), marking the start of the Yuan Dynasty of China. From the article:

"Founding of the dynasty

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Kublai Khan, Genghis Khan's grandson and founder of the Yuan dynasty
Instability troubled the early years of Kublai Khan's reign. Li Tan, the son-in-law of a powerful official, instigated a revolt against Mongol rule in 1262. After successfully suppressing the revolt, Kublai curbed the influence of the Han Chinese advisers in his court.[29] He feared that his dependence on Chinese officials left him vulnerable to future revolts and defections to the Song.[30] Khublai's government after 1262 was a compromise between preserving Mongol interests in China and satisfying the demands of his Chinese subjects.[31] He instituted the reforms proposed by his Chinese advisers by centralizing the bureaucracy, expanding the circulation of paper money, and maintaining the traditional monopolies on salt and iron, but rejected plans to revive the Confucian imperial examinations.[32]

In 1264, he transferred his headquarters to the Daning Palace northeast of the former Jurchen capital Zhongdu. In 1266, he ordered the construction of his new capital around that site's Taiye Lake, establishing what is now the central core of Beijing. The city came to be known as Khanbaliq ("City of the Khans") and Daidu to the Turks and Mongols and Dadu (大都, "Great Capital") to the Han Chinese.[33] As early as 1264, Kublai decided to change the era name from Zhongtong (中統) to Zhiyuan (至元). With the desire to rule all of China, Kublai Khan formally claimed the Mandate of Heaven by proclaiming the new Yuan dynasty in 1271 in the traditional Chinese style.[34] This would become the first non-Han dynasty to rule all of China.

The official title of the dynasty, Da Yuan (大元, "Great Yuan"), originates from a Chinese classic text called the Commentaries on the Classic of Changes (I Ching) whose section[35] regarding Qián (乾) reads "大哉乾元" (dà zai Qián Yuán), literally translating to 'Great is Qián, the Primal', with "Qián" being the symbol of the Heaven, and the Emperor. Therefore, Yuan was the first dynasty in China to use Da (大, "Great") in its official title, as well as being the first dynasty to use a title that did not correspond to an ancient region in China.[36] In 1271, Khanbaliq officially became the capital of the Yuan dynasty. In the proclamation of the dynastic name, Kublai announced the name of the new dynasty as Yuan and claimed the succession of former Chinese dynasties from the Three Sovereigns and Five Emperors to Tang dynasty.[37]

In the early 1270s, Kublai began his massive drive against Southern Song dynasty in South China. By 1273, Kublai had blockaded the Yangzi River with his navy and besieged Xiangyang, the last obstacle in his way to capture the rich Yangzi River basin. In 1275, a Song force of 130,000 troops under Chancellor Jia Sidao was defeated by the Yuan force. By 1276, most of the Southern Song territory had been captured by Yuan forces. In 1279, the Yuan army led by the Chinese general Zhang Hongfan had crushed the last Song resistance at the Battle of Yamen, which marked the end of the Southern Song and the onset of a united China under the Yuan. The Yuan dynasty is traditionally given credit for reuniting China after several hundred years of fragmentation following the fall of the Tang dynasty.

After the founding of the dynasty, Kublai Khan was put under pressure by many of his advisers to further expand the sphere of influence of the Yuan through the traditional Sinocentric tributary system. However, the attempts to establish such tributary relationships were rebuffed and expeditions to Japan (twice), Dai Viet (twice during Kublai's rule[b]), and Java, would later meet with less success. Kublai established a puppet state in Myanmar, which caused anarchy in the area, and the Pagan Kingdom was broken up into many regions warring with each another. In order to avoid more bloodshed and conflicts with the Mongols, Annam and Champa later established nominal tributary relations with the Yuan dynasty."