Establishment
In 699, the Tang government sent former Goguryeo Prince Go Deokmu, the third son of Goguryeo's last ruler, King Bojang, to Liaodong Peninsula, naming him "King of Joseon" and Governor of the Yodong Commandery of the Protectorate General to Pacify the East. Like his father, Go Deokmu had plans to rebel against the Tang and revive Goguryeo and provide a kingdom for the Goguryeo people.
The Tang Empire at the time was undergoing several crises, especially the An Lushan Rebellion.Along with these major events was also the pressure given by the Empire of Balhae. These and many other pressures allowed Go Deokmu to take full control of the Protectorate General to Pacify the East and establish a kingdom.
The Little Goguryeo kingdom was established during that year with Go Deokmu as its first king. Very little is known about how the establishment of Little Goguryeo was reacted upon by neighboring kingdoms. It is known that the Balhae was in good terms with Lesser Goguryeo in respect for the similar purposes that the two kingdoms possessed.
Read more about this topic: Little Goguryeo