Jang Bogo and Cheonghaejin (828): Silla's Maritime Trader

Jang Bogo was a Korean sea lord of the Unified Silla kingdom who in 828 founded Cheonghaejin, a fortified naval base on the island of Jangdo off Wando in south-western Korea. From there he suppressed the pirates who were seizing Koreans for the slave trade and built a commercial network linking Silla, Tang China and Japan. His rise from humble origins and his violent end make him one of the most striking figures of ninth-century East Asia.

Background: Silla and the eastern seas

By the early ninth century Unified Silla was in decline. Royal succession struggles weakened the court in Gyeongju, and provincial strongmen grew more independent. At sea, however, trade was flourishing. Korean merchants, sailors and monks settled in large numbers along the coast of Shandong and the Huai River in Tang China, in communities known as Silla quarters, with their own temples and officials.

The same seas were dangerous. Pirates, many of them Chinese, raided the Korean coast and carried off people to sell as slaves in China. The trade was serious enough that the Tang court issued orders against it.

From soldier to commander

Jang Bogo’s early life is obscure. He came from a humble family on the south-western coast, probably around Wando, and in Korean sources he is called Gungbok or Gungpa. The Tang poet Du Mu, who wrote a short account of him, calls him Zhang Baogao. As a young man he went to China, where he served as a junior officer in the Tang army in the Xuzhou region.

Around 828 he returned to Silla and asked King Heungdeok for permission to stop the slave raids. According to the Samguk sagi, the king gave him 10,000 men and the title of Grand Commissioner of Cheonghae, and he established a garrison on Jangdo, a small island guarding the sea lanes at the south-western tip of the peninsula.

Master of the sea routes

Cheonghaejin was well placed to control shipping between China, Korea and Japan. Jang Bogo’s forces cleared the pirates, and his fleet turned the base into a hub of trade. His ships carried goods such as Chinese ceramics, silk, books and luxury items, and he sent trading missions to Tang China and to Kyushu in Japan.

He also supported the Korean communities in China. At Chishan, on the Shandong peninsula, he founded the Buddhist temple of Fahua, which served Silla sailors and merchants. The Japanese monk Ennin, who travelled in China between 838 and 847, stayed there and received help from Jang’s network; his diary is one of the best sources on Jang’s activities.

Kingmaker and murder

Jang Bogo’s wealth and military strength drew him into Silla politics. In 838–839 he backed Kim Ujing, a claimant to the throne, sending troops under his ally Jeong Nyeon. They defeated the reigning king, and Kim Ujing became King Sinmu in 839, but died within months. His son, King Munseong, honoured Jang Bogo.

Jang then sought to have his daughter married to the king. The aristocracy in Gyeongju opposed the match because of his low birth. Relations broke down, and the court feared he would rebel. A former subordinate, Yeom Jang, went to Cheonghaejin pretending to defect and killed him. The Samguk sagi dates his death to 846, but Japanese court records indicate 841, a date many historians prefer. In 851 Cheonghaejin was abolished and its inhabitants moved inland.

Key people

• Jang Bogo (died c. 841): founder of Cheonghaejin and the leading figure in East Asian maritime trade of his time.
• King Heungdeok (reigned 826–836): authorised the garrison in 828.
• King Sinmu (reigned 839): placed on the throne with Jang Bogo’s help.
• Yeom Jang: Jang’s assassin, sent by the court.
• Ennin (794–864): Japanese monk whose diary records Jang Bogo’s network.

Legacy

Jang Bogo’s career showed how much power maritime trade could bring in ninth-century East Asia, and how hard it was for an outsider to break into Silla’s rigid bone-rank aristocracy. His fall left the seas open again to disorder in the decades before the end of Silla and the rise of Goryeo, whose founder also came from a sea-trading family.

In modern South Korea he is celebrated as a pioneer of trade and naval power. A Korean Navy submarine class and an Antarctic research station bear his name, and Wando hosts a memorial hall. The American historian Edwin Reischauer, who translated Ennin’s diary, drew Western attention to him as a remarkable merchant leader of the age.

Timeline

• Early 9th century: Jang Bogo serves in the Tang army.
• 828: He returns to Silla and founds Cheonghaejin with royal approval.
• 838: Ennin’s journey to China begins.
• 839: Jang’s forces help Kim Ujing become King Sinmu.
• c. 841: Jang Bogo is assassinated by Yeom Jang (846 in the Samguk sagi).
• 851: Cheonghaejin is abolished and its people moved inland.

Why it matters

Jang Bogo’s Cheonghaejin was one of the first maritime powers in East Asian history built on trade rather than conquest. His network linked the Japanese missions to Tang China, Korean diaspora communities and Silla’s coast, and it shows the importance of the sea in the medieval exchange of goods, people and ideas.