[2][3] Both Balhae remnants and miscellaneous tribal peoples like Jurchens lived in the area between the Yalu and Daedong rivers which was targeted for annexation by Goryeo.

The Jurchens switched allegiances between the Liao and Goryeo multiple times depending on which they deemed the most appropriate.

In one instance, the Goryeo court discovered that a Jurchen leader who had brought tribute had been behind the recent raids on their territory.

[8][9][10] As the geopolitical situation shifted, Goryeo unleashed a series of military campaigns in the early 12th century to regain control of its borderlands.

In 984, Goryeo failed to control the Yalu River basin due to conflict with the Jurchens.

However by the rise of the Wanyan clan, the quality of Goryeo's army had degraded and it mostly consisted of infantry.

[13][14] Yun Kwan believed that the loss was due to their inferior cavalry and proposed to the king that an elite force known as the Byeolmuban (別武班; "Special Warfare Army") be created.

It existed apart from the main army and was made up of cavalry, infantry, and a Hangmagun ("Subdue Demon Corps").

According to Breuker, Goryeo never really had control of the region occupied by the Nine Fortresses in the first place and maintaining hegemony would have meant a prolonged conflict with militarily superior Jurchen troops that would prove very costly.

The Nine Fortresses were exchanged for Poju (Uiju), a region the Jurchens later contested when Goryeo hesitated to recognize them as their suzerain.

This was because it had traditionally been part of their system of tributary relations, its rhetoric, advanced culture, as well as the idea that it was "bastard offspring of Koryŏ".

[21] The Jin went on to conquer the Liao dynasty in 1125 and capture the Song capital of Kaifeng in 1127 (Jingkang incident).

Having been defeated, Joseon was compelled to sever ties with the Ming and instead recognized the Qing as suzerain according to the imperial Chinese tributary system.