According to the legends, his mother Xiao Yanmujin dreamt that the sun fell from the sky and into her bosom, from which her pregnancy followed.

However, by the end of the ninth century, leaders of the powerful Yila tribe were expressing dissatisfaction with the Yaonian khans.

Abaoji became chieftain of the Yila tribe in 901, and in 903 he was named the Yuyue, commander of all of the Khitan military forces.

He started making a name for himself in 905 when he led 70,000 cavalry into Shanxi to create a brotherhood with Li Keyong.

His successes against the Han people in the north, against whom he had been raiding since 901, led to him receiving the support of seven tribal chiefs and even the acquiescence of the last Yaonian Great Khan.

[7] From 907 until 916, Abaoji was beset with constant uprisings and rebellions, mostly instigated by his own family members (cousins and brothers).

With his walled city showing off the tribe's wealth and power, he appointed all the usurpers to positions of influence which placated them.

Arguably the most important was the introduction of a dual administrative system in which nomadic steppe peoples would be governed by steppe traditions while sedentary populations in conquered Balhae and north China would be governed by a civil bureaucracy run largely on Han protocols.

While this did not receive universal support from tribal leaders due to the erosion of their own powers, this became the model that later steppe peoples would use to govern their diverse empires.

Five years later, the arrival of a Uyghur delegation led Abaoji to order his younger brother, Yelü Diela, to develop a new script on more syllabic principles.

On Li Cunxu's death, though relations between the two had soured, the proper forms were followed and an emissary was sent to the Khitan capital.

The souring of relations occurred probably due to the aggressiveness of Abaoji, as in 922 and 923 he had led an army deep into Hebei, looting and taking prisoners along the way.

He caught up with the Khitan ruler in Manchuria while he was on campaign against the Balhae kingdom and while he was encamped at Fuyu in present-day Jilin Province.

[3][16] Though Yelü Bei was designated heir apparent in 916, the empress dowager Shulü Ping did not consider him to be worthy and managed to have her second son Deguang succeed to the throne.