General Oi was a general who helped founding the Goguryeo

Goguryeo

Goguryeo or Koguryŏ was an ancient Korean kingdom located in present day northern and central parts of the Korean Peninsula, southern Manchuria, and southern Russian Maritime province....

, one of the Three kingdoms of Korea

Three Kingdoms of Korea

The Three Kingdoms of Korea refer to the ancient Korean kingdoms of Goguryeo, Baekje and Silla, which dominated the Korean peninsula and parts of Manchuria for much of the 1st millennium...

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Biography

Oi, Hyeopbo, Mari, and Jumong associated as a friend. Jumong made them his bodyguards and Oi's career started from this point.

Meanwhile, 7 sons of King Geumwa

Geumwa of Dongbuyeo

Geumwa was the second ruler of Dongbuyeo. , an ancient kingdom of Korea. His story is recorded in Samguk Sagi, Samguk Yusa and Book of King Dongmyeong.- Birth and background :...

 became jealous of Jumong, and Jumong was forced to leave Dongbuyeo

Dongbuyeo

Dongbuyeo was an ancient Korean kingdom that developed from Bukbuyeo, until conquered by the early Goguryeo, which then grew into one of the Three Kingdoms of Korea...

 with three friends. In 37 BC, Jumong became the first king of Goguryeo

Goguryeo

Goguryeo or Koguryŏ was an ancient Korean kingdom located in present day northern and central parts of the Korean Peninsula, southern Manchuria, and southern Russian Maritime province....

, and reunited all of the five tribes of Jolbon

Jolbon

Jolbon was a small, Korean tribal state which arose in the northern Korean peninsula from perhaps 1st century BCE.In 37 BCE, Jumong had fled from Dongbuyeo to avoid death at the hands of Dongbuyeo's Crown Prince Daeso, who presented great jealousy towards Jumong...

 into one kingdom. In 32 BC, Jumong sent General Oi and Bu Bunno (부분노, 扶芬奴) to conquer the Haengin state (행인국, 荇人國).

In 14, he and Mari attacks the Yangmaek state (양맥국, 梁貊國), and Gaogouli County

Gaogouli County

The Gaogouli County was one of three prefectures of Xuantu Commandery in southeastern Manchuria. It was established by the Han Dynasty after the fall of Gojoseon to keep Goguryeo tribes in check....

 in Chinese Xuantu Commandery

Xuantu Commandery

Xuantu Commandery was a commandery established beyond the far eastern pale of Han China. It was one of Four Commanderies of Han, established in 107 BCE, after the Han Dynasty invaded Wiman Joseon of Korea. Goguryeo rose in this area in competition with the Chinese over the region...

 during the reign of King Yuri

Yuri of Goguryeo

King Yuri was the second ruler of Goguryeo, the northernmost of the Three Kingdoms of Korea. He was the eldest son of the kingdom's founder King Dongmyeongseong. As with many other early Korean rulers, the events of his life are known largely from the Samguk Sagi.- Background :Yuri was the son...

, second ruler of Goguryeo, and eldest son of the King Dongmyeong (Jumong).