Bogo JANG was born in a coastal region of southern Silla in around 790AC, moved to the Shandong Peninsula of China in 810 to join the local military power the Muryeong Army of Xunzhou Province, and fought against a northern military group member Jeong-gi YI who was from Goguryeo (Kingdom of Korea).
張保皐は790年頃に新羅南部の海岸地帯に生まれ、810年中国の山東半島に渡り、その地の軍閥勢力であった徐州武寧軍に入って、高句麗人出身の北方軍閥・李正已と戦った。