장보고
Cheonghaejin was established originally as a military complex by General Jang Bogo in 828, the third year of King Heungdeok's reign. Jang appealed to Heungdeok to establish a military complex in Cheonghaejin to protect Silla's merchant fleets and coastal residents from pirates. He was granted permission and 10,000 troops. He established a small castle and a military base in Garipo.