장보고
One of the few sources on his early life is the 12th-century "Samguk Sagi" ("A History of the Three Kingdoms"), which contains a brief biography of Jang compiled three centuries after his death. The biography relates that Jang Bogo was adept in martial arts and claims that Jang's companion Jeong Yeon (정년, 鄭年) could swim five "li" (about 2.5 km) underwater, without taking a breath. The history further records that as young men the two companions, Jang Bogo and Jeong Yeon, traveled to Tang China. Their skills in horsemanship and the handling of spears soon won them military office. They were both named Junior Generals of Wuning District (武寧軍小將) (in what is today Jiangsu province).