King Taejo (claimed 47 – 165) was the sixth monarch of Goguryeo, the northernmost of the Three Kingdoms of Korea, from AD 53 to 146.
In 122, Taejo allied with the Mahan confederacy of central Korea and the neighboring Yemaek tribe to attack Liaodong, greatly expanding the realm of Goguryeo.
According to the Chinese historical work Book of Later Han (in volume 85), Taejo died in the year 121, and his son Chadae stepped up.
From viewing these historical facts, some scholars have come to the conclusion that the difference in surname was not a coincidence, but a clear indication that Jumong's immediate successors were not his descendants.
Another point of great interest among select scholars is the bestowing of the posthumous title of Taejo, which means "Grand Ancestor," on the sixth ruler of Goguryeo and not the first.
Scholars have therefore stated that this fact is further proof that different families ruled early Goguryeo before the consolidation of power under King Taejo.