President Lee Jae Myung, center left, encourages crew members during a visit to the 3,000-ton submarine Shin Chae-ho at the Navy Submarine Command in Changwon, South Gyeongsang Province, May 26. Courtesy of Cheong Wa Dae

The Navy has named a new submarine after a historical diplomat and christened a new frigate after a key hub city south of Seoul, the armed service said Friday.

The second vessel of the 3,600-ton Jang Yeong-sil-class KSS-III Batch-II submarine program has been given the name "Seo Hui," after an eminent diplomat from the early years of Goryeo Dynasty (918–1392), the Navy said in a release.

Seo Hui (942-998) is best known for his brilliant diplomacy that averted war with the Khitan forces, who then ruled present-day northern China. His achievements helped Goryeo secure its strategic six provinces east of the Amnok River.

The fifth vessel of the 3,600-ton FXX Batch-III frigate program has been named "Pyeongtaek," after an industrial city in Gyeonggi Province surrounding Seoul, also home to the Navy's Second Fleet.