Jang Bogo came originally from Silla's coastal region. As a young man, he crossed to Tang China together with his friend Jeong Nyeon, and rose to the rank of junior general in the Wuning Army stationed at Xuzhou. When he later returned to Silla, he witnessed firsthand how Tang pirates were capturing Silla civilians and selling them into slavery, and he petitioned King Heungdeok for permission to establish a military garrison to put a stop to it. The king granted his request, and in 828 (the third year of King Heungdeok's reign), Cheonghaejin was established on what is now Jangdo Island, in Wando County, South Jeolla Province.
Cheonghaejin began as a military and maritime base charged with guarding against pirates and protecting sea routes. From it, Jang Bogo exercised considerable influence over trade and Silla communities linking Silla, Tang China, and Japan. Claims that he “monopolized” East Asian maritime trade or built a “trading empire” are later rhetoric, not a verifiable market-share fact. It is more accurate to describe Cheonghaejin as a powerful base combining military, commercial, and diplomatic functions.
Excavations from 1991 to 2001 identified rammed-earth walls, building sites, a well, coastal timber rows, and a U-shaped stone structure interpreted as an access or landing facility. Wando County reports about 30,000 finds, roughly 890 meters of wall, and 331 meters of coastal timbers. These remains show an occupied base where people, vessels, and supplies were managed; they do not prove every later claim about a maritime “empire.” Visitors should read the channel, tidal flats, defenses, and approach route together, then compare the artifacts at the Jang Bogo Memorial Hall. Access can change with construction and tides. This story separates excavated evidence, documentary history, and later heroic language.